Arthur was the Fourth Main Antagonist in the series, and one of the most dangerous. His pattern was to carry out a kill cycle roughly once a year (occasionally twice). Arthur was the only antagonist to have successfully killed for three decades, while remaining hidden in a perfect cover life. He was thought by the FBI to be a mere "myth" chased by Special Agent Frank Lundy.
Note: There are two errors in the above video:
- The kill count is incorrect.
- Arthur did not tell Dexter that he had killed Rita.
After the discovery of a pattern of killings by Special Agent Frank Lundy, the unknown killer was dubbed Trinity or The Trinity Killer, due to the initial thought that each kill cycle involved three murder rituals. It was later discovered by Dexter Morgan that it was actually four murders per cycle, not three. The 'missing' ritual involved the live burial of a 10-year-old boy at the beginning of each cycle ("Lost Boys").
During the past fifteen years, Frank Lundy had counted 15 kill cycles (per "Blinded by the Light"). When Lisa Bell was murdered (in "Living the Dream"), Lundy learned of an additional fifteen years, dating back to Vicky Noonan in 1979. This likely made Trinity's kill count much higher.
Trinity usually did not kill outside of his well-established cycle, and generally posed no threat to anyone around him once the cycle was completed There were exceptions to this, such as Kyle Butler. He also frequently terrorized his family members.
Trinity has been widely polled by viewers of DEXTER as the ultimate antagonist in the series, despite his objectionable methods of murder. His popularity might be due to actor John Lithgow's superb portrayal of the killer, which earned him a Golden Globe award and an Emmy award.
Before Arthur died, he was a man in his early 60's with white-gray thinning hair, blue eyes, as well as an imposing height and build. In spite of his age, Arthur possessed a considerable amount of strength, which was seen when he subdued a strong individual like Dexter in a chokehold and overpowered his athletic son, Jonah, with startling ease.
When on the job (at the dig sites), he preferred a T-shirt and blue jeans, as well as work boots and equipment used for the dig. When teaching at school, he wore much more formal attire befitting his occupation as a teacher. This formal attire was also seen when he went to church. This could include tan colored or grey suits that remained unbuttoned. He also frequently wore mirrored sunglasses.
On the night that he kidnapped Tarla Grant, he wore dark clothing. When he bludgeoned Earl Doorman, he wore a blue jumpsuit, along with a face shield and plastic gloves, to prevent the blood from spraying onto him.
Being "born in blood" (Dexter's euphemism for psychological trauma leading to homicidal impulses), coupled with Arthur's longevity as a successful serial killer, made this man incredibly complex. Arthur's life was comprised of schedules, routines, and identical kill cycles. If something did not go according to his plan, he found it difficult to improvise. Possibly due to his age or his increasing lack of humanity, the boundaries compartmentalizing his life started to crack. His moods would switch at random, and he was easily angered. As quoted by Dexter himself, "Yesterday he was jumping down my throat...today he is a happy dancing man. Is that mask of his crumbling?"
The Family Man
Dexter: "A wolf in sheep's clothing. Hour by hour the spitting image of a normal man. Up at 6 AM. Breakfast 7 at AM. Work - 8:30. A study session shaping young minds...even on a Saturday. Noon lunch with Faculty, out at 3:00. Dinner at 6:00. Father, husband, teacher, Deacon...all in the name of blending in. Camouflage is nature's craftiest trick."
Arthur lived a nearly perfect cover life. He masqueraded as a Church-going family man that was adored as a beloved teacher, husband, father, and model citizen who helped the community through an organization known as Four Walls One Heart, which built homes for the homeless. To the general public, he had survived as a kind gentleman for decades, perfectly hiding his true face while using the traveling nature of Four Walls One Heart in order to confirm where he would start his next cycle of kills, before returning home for a "cool-down" period. Because he was a teacher, he took advantage of school holidays for his extra-curricular 'activities. Despite his public displays of love for his family, he was controlling and abusive in the home.
Aside from the murders that he committed, the violent part of Arthur came in the form of outbursts and tirades toward his family. Sally, his wife, would do everything that he demanded, fearing that he might harm her or their children if she didn't. She would even show affection for him, both in private and public, in her effort to keep him happy. Arthur was capable of treating his family nicely behind closed doors, as long as they did nothing to annoy him..
He was especially controlling with his daughter, Rebecca, who he called Vera (the name of his dead sister). Arthur often locked Rebecca in her bedroom, which was decorated for a young child. The door had bolts on the outside and the windows were unable to be opened. This was not usually a punishment, but to insure that she was "protected."
Jonah Mitchell took the brunt of Arthur's abuse. Arthur could not control his anger whenever Jonah irritated him. He was shown hitting Jonah, choking him, and destroying his sports' trophies. He even broke Jonah's pinky finger after he damaged Arthur's car. Jonah both feared and hated his father. At times, Jonah dared to fight back, either verbally or physically. This enraged Arthur.
When it came to his other daughter, Christine Hill, he treated her in two fashions. He only allowed Christine to see him on holidays or her birthday, but he would act like a caring father. While he was out of town with Four Walls One Heart, he often sent her post cards, signed with "Wish you were here." However, when Arthur became frustrated with her, he called her names behind her back. He then completely shut her out of his life, which devastated Christine. When Dexter told Arthur of Christine's suicide, he appeared sad, but called her "weak."
Sorrowful Lone Boy
With his original family long gone in a tragic past, Arthur often reminisced about his sister, mother, and father. In memory of his sister, he would leave a smudge of her ashes at his kill sites. He was very protective of his sister's ashes and, when Jonah destroyed her urn, Arthur flew into an immense fit of rage. His ongoing relationship with his father was the most dramatic. Before he bludgeoned a man, he would share a drink with his long dead father, across from an empty chair. Arthur then willed himself to go to a local bar just to have himself beaten senseless, while yelling insults at his attacker. This likely represented the abuse that he had endured from his own father. For his mother, he lamented the loss of her from suicide at such an early age. After he forced the third person (a mother) in the cycle to fall to her death, he would call her "Mommy" and briefly grieve.
The first victim in Arthur's kill cycle was always a ten-year-old boy, which represented Arthur himself. In "Lost Boys" Arthur was shown approaching a young boy, pretending to be a police officer. He pulled it off with a fake badge and by saying that the boy's parents were in an accident. The boy initially went along willingly. After the boy was lured to his van, Arthur sedated and abducted him. The boy was taken to a hidden buried shelter. For a few days, Arthur attempted to play trains with the boy, while constantly calling him by his own name, as if he were the child himself. The boy repeatedly told Arthur that his name was Scott, not Arthur. During this time, Arthur acted very innocent and never harmed Scott. However, he refused to let Scott have food unless he put on a set of PJs similar to the ones that he had once worn. Eventually, Scott agreed to be called Arthur. This delighted Arthur and he told Scott that it was time to set him free. He then gave Scott a cup of drugged ice cream, which caused Scott to pass out. Arthur moved the unconscious boy to a Four Walls One Heart dig site, and began to cover him with cement. This would, in Arthur's troubled mind, preserve the boy's innocence. However, Dexter arrived in time to rescue Scott before he died.
Arthur became very defensive when Dexter called him a pedophile, likely because he viewed a child as a manifestation of the innocence that he once had, and he couldn't bear to think of a child being hurt (even though he didn't hesitate to kill one).
The Caring Brother
The second victim in Arthur's cycle was always a young, single woman who represented his sister, Vera. After breaking into her house, he would ambush her in the bathroom and strip her naked, along with himself. He would force the young woman into the bathtub with him and keep her subdued with a sleeper hold. He then sliced her femoral artery with a straight razor, which caused her to bleed to death. As she died, he would watch the woman's face in a hand mirror, thus signifying the way his sister had looked at him while she died years before ("Living the Dream"). After he finished the kill, he left traces of his sister's ashes at the crime scene, with the dead woman pointing at them. Arthur would then take a shower hot enough to burn himself, most likely to wash off his sins and mixed emotions.
The Forgotten Son
The third personality for a middle-aged woman with two children in the killings, Arthur would find a woman matching the age of his mother that is the parent of two others, much like himself and his own sister. He would first meet up with the woman and pretended to be a kind old gentleman either walking a dog or some other mundane task, just so that he could introduce himself to them and learn a little about them. Here he adopted the simple personality that just about anyone can fake - common courtesy and small talk. Afterwards, he'd drop the act and find a way to get her alone, threatening her as he makes her drive to a tall abandoned building. From here it's all based on his orders and her voluntary choice, that is, unless she refuses to comply. As the two of them reach the spot where she's supposed to jump from (just like his mother did), he'd urge her to fall back based on her own will. If the woman did not want to, he'd start to tell her that he'd make her children suffer if she does not follow his orders, to which she'd eventually let herself fall and die. Arthur would then leave traces of ash here, after feeling an immense flood of emotions hit him.
Father Vs. Son
The fourth personality for an older man with possibly two children in the killings, Arthur would locate a father matching the age of his own father. Because not every one of his victims was a drunkard, he'd need to find someone else to take half of the ritual in this kill by taking out their drunken fury on Arthur with multiple punches and kicks while he insults them (much like his own father would do to him back in his past). After that was finished, he'd start stalking another man to an area and start yelling insults at them as he bludgeoned them with some type of weapon (after a recommendation from a local store owner, it becomes a hammer). During this entire process, he could be portrayed as a very vulnerable man fighting back against his father, despite the fact that his victim was the one on the defense in this situation. Once again, Arthur would leave trace evidence of ash after he's finished killing the man and would start to sink back into reality.
The True Arthur
Arthur always had a hard time accepting who he truly was and, when he was faced with the option to kill something (such as a deer), he began to cower, as if he had never picked up a weapon before. This could have suggested a slight crack in the already unstable persona he lived with, further proving that he never really took pride in his killings. It is more than possible that, by doing what he did, Arthur attained a specific recollection of the events of his childhood and was simply trying to prove how 'innocent' he was, even in such an indirect and sinful manner.
Arthur, in all reality, disliked the demon within himself and had lost control of his life because of it - So much so that he'd been contemplating ways to stop it, to kill the demon...in killing himself. Little to Dexter's knowledge, Arthur had been building his own coffin as of late and wished to end his own life in order to stop the monster...thus a planned trip was made to a Tampa dig site where he could jump to his death much like his mother. After finding out more from Dexter, he learns that he killed a man (though Arthur believes it to be accidental) and thus begun sharing his past...to relay to someone finally about who he truly was from the past, though did not reveal to Dexter personally that he kills people.Arthur changed drastically at this point, becoming almost ecstatic about his newfound "friend" and went overboard by becoming too open to try and make families listen to him while meeting plenty of people. In a way, it could be that Dexter was officially Arthur's way of confessing to his sins without actually saying them and he was happy to be free of them, ready to take his own life. Later on, as Dexter prepares a kill room and attempts to nab Arthur in his room, he finds him missing and so goes to the Four Walls Build to find him. Unbeknownst to him, Arthur was planning to kill himself all along and relieve himself of the demon inside him. Ironically, Arthur's suicide plan prevented his death at the hands of Dexter, as Dexter noticed him trying to jump off of a building and purposely saved his life, just so that he can have him on his own table. Arthur then begun to act as if new life has been breathed into him and praised Dexter, having believed that God saved his life. However, it was soon revealed that Arthur had returned to his previous personality, no longer wanting to end his own life, but continue in his bloodthirsty ways...
The true Arthur only appeared when Dexter (first playing as Kyle Butler) found out just how far Arthur would go in his acts of violence. After a mishap involving Dexter almost killing Arthur in his own home, Arthur forced his next cycle to begin early...thus kidnapping a child for his next kill. During this time, the two played cat and mouse, with Dexter trying to find Arthur, while the latter was dangling the boy's life at the end of a thread without revealing anything about his process. When Dexter finally figured it out, as well as the location of where the boy would die, the two confront one another, but Arthur manages to escape...from here on moving onto the hunt.
When on the hunt for who Dexter really is, he was shown to be a cold and calculating man that would use bait to find out what he needs. He did, however, talk in a more relaxed, almost cheery voice as if he was enjoying this game. In due time, he finally figured out where Dexter works and met him face to face in the Homicide department...a true stareoff occurring between the two. After a threat here and there, Dexter tailed him to a garage and attempted to set him up for his own Ritual. However, he ended up failing when caught up in an ordeal with some sheriffs. When Dexter returned to the van where he left an unconscious Arthur, he found nothing but an empty space where he once was.
Arthur took pride in the vehicle that he possessed, becoming highly infuriated with Jonah for damaging it beforehand. After taking the windshield clean off, he got it fixed and painted up nicely. Of course, during this time, he acted out his revenge on Dexter for not only stopping his cycle, but also attempting to kill him earlier. In a break of the cycle that was technically still a part of the normal order (even though the boy survived, he moved on to the woman in the bathtub, though he chose to combine that kill with the third kill of an older woman with two children), he goes to Rita's house and sets her up for a kill just like his second in order...slashing her thigh and allowing her to bleed out within a bathtub. This proves that, in a fit of rage with his passenger, he needed to leave something behind to show Dexter punishment after his attempted escape from Miami.After killing Rita and feeling accomplished, Arthur picked up his vehicle and drove off with a smile on his face...truly feeling like he was getting away with murder for the very first time, rather than just trying to please his Dark Passenger that always called to him. However, Dexter had secretly sabotaged his car, removed the oil cap and hid in his trunk, in order to capture and kill him. It is here that Arthur expressed everything that is true about him. He says that he never took pride in his killings (unlike Dexter), but only had to because he couldn't control his urges. He craved to be free of them, to be stopped without trying...and then lamented that his plan to be stopped by praying for it to happen finally worked because Dexter arrived and finally did exactly that. Arthur began to show remorse for his murders and only wishes to be set free of his Dark Passenger, as he accepts God's will in all of this. He then went on to say that it's already over, and Dexter is baffled, as he couldn't understand what Arthur meant by that statement. He concluded that Arthur had to be referring to his killing spree, basically accepting his own death, but it is likely that he was actually referring to Dexter's desire and ambition to become a good family man, but what Dexter didn't know was that this goal was already prevented by the death of Rita. Arthur then noticed his train set and record player, asking in his final moments if he could hear his train and music play before he gets killed, which suggested a return to his innocence once more and a hope to die peacefully.
Just before his death, Arthur seemed to accept that his rampage was justly halted. He predicted that, eventually, the same would happen to Dexter, knowing that he had destroyed Dexter's family life which was his means of keeping his humanity
Arthur Mitchell was born in Tampa, Florida, and lived in a two-story blue house for most of his young life. He grew up just like any other boy would -- that is, until one day in 1959. As a curious ten-year-old boy, he stood in the bathroom doorway, watching his sister, Vera, take a shower. When his sister noticed him in the mirror, she was startled and slipped, shattering the shower doors. A shard of glass sliced her leg and she bled out in front of him. By the time the ambulance came, she was dead. This graphic scene of violence scarred Arthur forever, and came as a hard blow to the entire family. For a year after the incident, his mother, Marsha, grew increasingly depressed, culminating in her suicide by jumping off a bridge in 1960. This left Arthur alone with his father, Henry, a drinker who became verbally and physically abusive to him. Henry blamed him for the deaths of Vera and Marsha, and frequently called Arthur a pervert. In 1964, Henry was found bludgeoned to death in an alley near a bar (presumably by Arthur himself, who would have been 14 or 15 at the time).
What happened to Arthur after his father's death is not revealed. It's possible that he had relatives who took him in, or that he was somehow emancipated. After graduating college, he became a teacher in his hometown and met Lorraine Hill, who later conceived his first daughter. Arthur would eventually join the organization known as Four Walls One Heart, which he would use as his alibi when starting his kill cycles. One night, his young daughter, Christine, witnessed Arthur, through a window, murdering a woman in a bathtub. She never told her father what she saw until thirty years later, when Lisa Bell was murdered in the same house. After Arthur's relationship with Lorraine ended, he and Christine became estranged, only meeting on holidays and her birthday. (Arthur would later tell Dexter that it was because of his habit of pushing people away.) Through the years, Arthur often sent Christine postcards from his trips away with Four Walls One Heart, each one saying, "Wish you were here. Love, Daddy."
Some twenty years before Season Four, Arthur met his future wife, Sally Mitchell. After marrying, they had two children, Jonah Mitchell and Rebecca Mitchell. He continued to raise this family, work as a long term teacher, and commit to various community activities. Behind closed doors, his moods were unpredictable. He would often imprison his daughter in her room, and abuse his son and wife. They did whatever was necessary to keep Arthur happy. His family looked forward to the times that Arthur went out of town with the Four Walls One Heart organization. Often these were the locations where Arthur carried out a kill cycle. First, Arthur would bury a boy at the dig site. Soon after, he would kill three other victims, each in a different way. He then returned home, cheerful and relaxed.
At some point in time, FBI Special Agent Frank Lundy caught onto the similarity of the kill cycles and dubbed the unknown killer, "The Trinity Killer." Arthur wasn't aware that someone had connected his killings and figured out his pattern. Because Lundy could not convince the FBI that The Trinity Killer existed, he would effectively chase a "ghost" across the country, never knowing who Trinity was until it was too late.
Arthur Mitchell was a middle-aged serial killer who has been active for three decades without being noticed. Agent Frank Lundy , the FBI's lead investigator of his crimes, has dubbed him "The Trinity Killer" because it was believed that he killed in threes. However it has since come to light that he in actuality kills four victims every cycle (Lost Boys). His M.O. is to kill a series of four people in a very specific fashion. The first victim is a young boy, usually around the age of 10, whom he forces to wear pajamas then buries him alive in wet concrete. The second victim is a young woman whom he holds down in a bathtub, cuts the femoral artery and uses a mirror to watch die from bleeding out. The third victim is a mother of 2 kids whom he uses threats to her family to convince to jump off a building to her death. The fourth victim is an older man, also a parent of two children, whom he bludgeons with a hammer. He's immaculate, always careful never to leave any trace of his presence at the scenes of his crimes aside from the trademark ash smudge he leaves his victims pointing to. Through his killings, he's recreating the traumatic deaths of his own family members (If I Had a Hammer). He performs this cycle roughly once or twice every year, during school breaks. His first cycle took place in Miami. 30 years later (Living The Dream), he returned to exactly the same locations and killed there again.
In Road Kill, Arthur revealed his back story to Dexter. When he was 10, in 1959, he walked in on his sister, Vera, showering. When she saw him and panicked, she slipped and smashed the shower doors' glass, her femoral artery being slashed in the process. His mother, Marsha, then became very depressed and killed herself the following year by jumping off a roof. His father, Henry, started drinking heavily, became more abusive and beat Arthur as a result of these deaths, blaming him for them. He too was killed in 1964 when he was bludgeoned to death with a hammer in an alley (Dexter theorizes that Arthur himself was the killer. He would have been 15 at the time). The first victims of the cycles, the young boy dressed in a pajamas and placed in wet concrete, is supposed to symbolize Arthur himself on the night of Vera's death, his last moment of innocence.
Despite Arthur's serial killing, he still manages to maintain a family life with his wife, Sally, and two children, Jonah and Becca, who he genuinely loves. He works as a high school teacher and is also a deacon and the leader of Four Walls, One Heart, a charitable Christian home building organization, which he uses as a cover for his travels throughout the country. He keeps his home building plaques as trophies for his killings. It was, however, revealed in Hungry Man that Arthur is extremely controlling, domineering and even verbally and physically abusive, his family keeping up the facade of a happy suburban family. He also has an adult daughter, Christine Hill, from a past relationship. In Dex Takes a Holiday, she shot Debra and Lundy, killing him, in order to protect Arthur; when she was five, she had witnessed him performing one of his bathtub murders. It was initially believed by some that Arthur had been the shooter and by some that Nikki Reed, one of the Vacation Murderers, did it. Eventually, Christine was caught and killed herself after confessing.
Because Arthur had apparently escaped (and was never known to have been killed), the FBI continued to chase after a ghost, while his family lived within the Witness Protection Program. To this day, the only ones that know Arthur is actually dead are Jonah Mitchell and Dexter himself. (Dexter told Isaak Sirko and Debra Morgan that he had killed his wife's murderer, but both Isaak and Debra are now dead.)
In Arthur killing Rita Morgan, he created a downward spiral for Dexter that followed him for quite some time. To escape the depression he was hit with, Dexter impulsively killed a man named Rankin who insulted his late wife. He then tried to feel alive again by hunting a man named Boyd Fowler. This led to an encounter with a woman named Lumen Pierce. After he gained Lumen's trust, he learned that she was a victim of rape and torture by the Barrel Girl Gang, which was led by Jordan Chase. (Later, Jordan told Dexter that he had followed the Trinity Case very closely.) Feeling responsible for Rita's death, Dexter attempted to redeem himself by aiding Lumen in her quest for vengeance. Together, Dexter and Lumen began to kill the members of the group, one by one. Along the way, they became romantically involved but, upon killing the last man, Lumen's desire to kill vanished, and she saw a future with Dexter as impossible; thus, she left him.
During the Doomsday Killer Investigation, Lieutenant Debra Morgan received information that both Arthur's wife and daughter were found dead in Nebraska. They appeared to have been murdered in ways similar to how Arthur killed his victims. The FBI, after interviewing the only surviving family member, Jonah Mitchell, began to investigate the possibility that Trinity had returned. Dexter (knowing that Arthur was dead) left for Nebraska to find out what actually happened. In a confrontation with Jonah, Dexter learned that Rebecca had committed suicide, due to living under high pressure from their mother. Jonah then killed their mother out of anger. Dexter initially planned to kill Jonah, feeling that he had gone down his father's path. However, after Jonah showed remorse, Dexter told Jonah to forgive himself, and chose not to kill the only remaining member of the Mitchell family. ("Nebraska")
Cycle of Kills
Due to his life as a teacher, Arthur Mitchell's cycles took place during school holidays, while out of town with Four Walls One Heart. The plaques he received for his part in building new homes served as his trophies.
- The 10-year-old boy represented an "innocent" Arthur, before he witnessed the death of his sister. Arthur would bury a boy in wet concrete within the foundation of a house at a Four Walls One Heart site. It was Arthur's way of symbolically preserving his own innocence that he had lost during the incident with his sister.
- The woman bleeding out in the bathtub represented Arthur's sister, who accidentally died while she was taking a shower. Arthur had startled her and she fell, breaking the shower doors, and cutting her femoral artery.
- The woman jumping from the building represented the suicide of his mother, who became depressed after her daughter's death. Arthur was extremely particular about making a woman fall on her own, rather than him pushing her.
- The final kill represented the death of his father, who was bludgeoned in an alleyway. It was arguably Arthur's most violent and sadistic kill in the cycle, because of his deep hatred for his own father, who had abused him.
- 2006 September 10 - Mark Wolter (age 10)
- 2007 August 11 - Thayer Copperud (age 10)
- 2008 September 15 - Brody Avenir (age 10)
- 2009 July 9 - Mathew Hicks (age 10)
- 2009 September 16 - Christopher Kavanaugh (age 10)
- 1979 - Vicky Noonan (age 22)
- (Missing years)
- 1993 March 12 - J. Lewitt
- 1994 September 5 - I. Rosengard
- 1995 February 26 - A. Darakjan
- 1997 February 12 - Loretta Kellerman
- 1997 September 16 - M. Bogert
- 1998 August 23 - L. Candace
- 1999 March 9 - J. Spaan
- 1999 October 7 - H. Grodman
- 2000 March 3 - Anita Soloman
- 2001 March 11 - L. Fisher
- 2002 October 24 - R. Goldman
- 2003 April 15 - K. Watkins
- 2005 May 11 - A. Goff
- 2006 September 18 - J. Meltzer
- 2007 July 20 - R. Cornelius
- 2007 August 16 - Tamera Klaman
- 2008 July 20 - L. Spheeris
- 2008 September 9 - Julie Hillard
- 2009 September 21 - Lisa Bell
- 1993 March 17 - D. Webster
- 1994 September 10 - E. Hemming
- 1995 March 3 - N. Reiss
- 1997 September 21 - J. Snisse
- 1998 August 28 - R. Elliot
- 1999 March 14 - R. Golden
- 1999 October 14 - C. Endless
- 2001 May 16 - P. Ford
- 2002 October 29 - J. Lewis
- 2003 April 20 - A. Asarcca
- 2005 May 16 - L. Pickford
- 2006 September 23 - J. Antonoff
- 2007 July 25 - R. Hermosillo
- 2008 July 25 - J. Leiberman
- 2009 September 26 - Tarla Grant (age 36)
- 1993 March 22 - S. Hunter
- 1994 September 15 - J. Roberson
- 1995 March 8 - D. Freiburn
- 1997 September 26 - E. Newman
- 1998 September 2 - R. Dermott
- 1999 March 19 - B. Ball
- 1999 October 19 - F. Calvert
- 2001 May 21 - A. Severse
- 2002 November 3 - C. Moreno
- 2003 April 25 - J. Jones
- 2005 May 21 - A. Roman
- 2006 September 28 - J. Ellis
- 2007 July 30 - B. Polaski
- 2008 July 30 - R. Bear
- 2009 October 1 - Earl Doorman
The following victims are the few kills that Arthur has made outside of his kill cycle.
- Henry Mitchell - Arthur's father. Although it was never confirmed, due to the profanity that Arthur shouted while bludgeoning the men, it was probable that Henry was Arthur's first kill.
- Kyle Butler - His name was the same as Dexter's alias. Arthur was caught by Kyle breaking into his home. When Kyle threatened to call the police, Arthur killed him in order to silence him. This was done after Arthur had failed at starting a new cycle.
- Rita Morgan - A bathtub victim. She was not part of a cycle for two reasons. Arthur had yet to succeed in burying a young boy in cement, and Rita wasn't a young, single woman. When Arthur found where Dexter lived, Rita became a victim of circumstance. Of special note, Arthur was the second Main Antagonist to kill a main character in the series (with his final victim being Rita Morgan). Before that, only Lila West had killed a main character - Sergeant James Doakes.
- Vera Mitchell - She was startled by Arthur while she was in the shower. She fell, broke the shower doors, cut her femoral artery, and bled out.
- Frank Lundy - He was shot by Christine Hill, who tried to save her father from being caught.
- Stan Beaudry - He was killed by Dexter because he needed someone to frame for Trinity's murders.
- Rebecca Mitchell - She committed suicide in a fashion similar to the bathtub victims.
- Sally Mitchell - She was killed by Jonah Mitchell because her abusive behavior was the reason for Rebecca's suicide.
- Jonah Mitchell
- Scott Smith
- Kyle Butler
- Debra Morgan - indirect attempt; shot by Christine Hill, but survived
- Frank Lundy - He was believed for some time to be a victim of Trinity, until it was confirmed that the person who shot Lundy and Debra Morgan was shorter than Trinity.
- Rebecca Mitchell - She actually committed suicide in a bathtub, although Debra thought that Trinity was the one to blame.
- Sally Mitchell - She was killed Jonah Mitchell, but Debra also believed her to be a victim of Trinity.
- Stan Beaudry - It was never mentioned, but because Dexter had planted Arthur's DNA in Stan's garage and truck, the police may have later linked Arthur to Stan's disappearance.
|First theme music for Trinity|
|Trouble with the audio sample?|
His theme music is later used in Season 6, Episode 7, when Debra tells Dexter about the murder of Trinity's wife and daughter and when Jonah walks towards Dexter, as well as in Season 7 for Ray Speltzer.
- The name of Trinity's character was incorrectly listed on the IMDb as Walter Simmons (rather than Arthur Mitchell).
- Arthur's wife's name is Sally, which was the name of the sister of John Lithgow's character in 3rd Rock from the Sun.
- Both John Lithgow (Arthur) and Julie Benz (Rita) have each appeared in Sylvester Stallone's movies. Lithgow played the main antagonist in Cliffhanger, while Benz appeared in Rambo, playing a damsel in distress.
- Arthur was the only main antagonist to be killed by Dexter in a full ritual. He was wrapped in plastic in a kill room, surrounded by photos of his victims. After his blood was taken, he was dismembered, and dumped into the Gulf Stream. Afterward, Dexter placed his blood slide inside his (second) slide box.
- Brian Moser didn't have a blood slide taken, and his body was left for the police to find.
- It is unknown what Dexter did to Lila West's body after killing her, but he didn't take a blood slide from her.
- Miguel Prado was killed in an M.O. similar to George King's, so he didn't have a blood slide taken.
- Jordan Chase was dismembered and dumped into the Gulf, but he didn't have blood taken, and most importantly, was not killed by Dexter, but by Lumen Pierce. He was also the last main antagonist to be dismembered.
- Travis Marshall was killed and had a slide taken, but since Debra walked in on Dexter, he was not dismembered or disposed of properly. Instead, with Debra's help, Dexter burned Travis' body and made it look like a ritualistic suicide, leaving it for the police to find. Dexter also lost the blood slide at the crime scene, which was later found, broken and partially burned, by Maria LaGuerta. Also, Travis was the last person Dexter took a blood slide from, as he later abandoned this practice when Debra discovered that he was a serial killer,.
- Isaak Sirko, although not killed by Dexter, was presumably dropped into the Gulf Stream, where Dexter took him so that he could be with Viktor Baskov, Isaak's lover, and a previous victim of Dexter.
- Oliver Saxon was killed in a police station, in self defense, so his body was presumably autopsied and later buried or cremated.
- Interestingly, Arthur was the first main Antagonist to be dumped in the Gulf Stream. Dexter dropped the hammer to Arthur's face in one shot, and then Dexter was shown throwing bags containing Arthur's remains overboard.
- He was the oldest main antagonist in the series, as Professor Gellar was technically not the main antagonist of Season Six, despite being 65 at the time of his original death (which was prior to the events of that season). Walter Kenney was the oldest known victim overall, being killed at age 73.
- He was the first antagonist to affect Dexter's life partially (since he killed Rita, and Dexter grieved for her throughout season 5). The second to do so was Oliver Saxon, the antagonist of Season 8. He killed Dexter's protege, Zach Hamilton, killed the woman who originally made the code, Evelyn Vogel, and shot Debra, which led to her brain death and giving Dexter a reason to mercifully kill her.
- Travis Marshall was close to doing the same, as he threatened to kill Dexter's son, Harrison, but failed to do so. Isaak Sirko held Hannah McKay hostage but fully intended to let her go free if Dexter helped him and Maria LaGuerta nearly had him arrested for being the Bay Harbor Butcher but failed and she could have also brought down Debra Morgan.
- Arthur was the second person who found out that Dexter was using an alias around him, and discovered his real name; the first one was Zoey Kruger.
- He was the second main antagonist to be married (the first being Miguel Prado), and the first (and only) to have children. That said, it is unknown whether or not Stan Liddy was ever married or had children, as he is in his late 50's and very little is known about his past.
- Arthur was the first main antagonist of the series who was not only present in all episodes of the season, but was also a threat throughout. Season 1's Brian Moser, while being the central threat throughout the season, did not appear in all of its episodes. Season 2's Lila West was absent for the season's first two episodes. Season 3's Miguel Prado, while appearing in all episodes of the season, only appeared as a corpse in the season finale, and thus did not serve as a threat then.
- In addition, Season Five's Jordan Chase did not appear until halfway through the season. Season Six's Travis Marshall was shown to be a protagonist for a majority of the season, only to be revealed as the main antagonist (to even himself) near the end. Season Seven's Isaak Sirko died nine episodes into the season, dying as a protagonist rather than antagonist. Maria LaGuerta was a main protagonist for the first six seasons and slowly became a main antagonist for the seventh season, becoming a real threat after Isaak's death (though not linked).
- He introduced himself to Tarla Grant as Alan. It could be a reference of Alan Grant, the main protagonist of Jurassic Park movie.
- Both of his daughters committed suicide - Christine Hill and Rebecca Mitchell.
- It is remotely possible that parts of Trinity's character were based on Dennis Rader, the BTK (Bind, Torture, Kill) killer. Both held prominent positions in their churches; both had a family; and finally, both of them had a specific routine they followed. Trinity's process could be considered a more drawn-out version of BTK's murders, with the cement burials being the binding, the bathtub kill being the torture, and the last two being the kill..
- Arthur's first name is coincidentally the middle name of his actor, John Lithgow.
- Trinity Case
- The Trinity Killer
- Vera Mitchell
- Sally Mitchell
- Jonah Mitchell
- Rebecca Mitchell
- Arthur Mitchell's House
- William Moseley High School
- Walter Kenney, The Tooth Fairy Killer, a similar older serial killer