Arthur was an unassuming suburbanite man who had been living a double life as one of America's most prolific and deadly serial killers for three decades. Each of his kill cycles included four distinct rituals. He was thought by the FBI to be a mere "myth" chased by Special Agent Frank Lundy.
The Trinity Killer
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 victims. 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 ten-year-old boy at the beginning of each cycle ("Lost Boys").
During the past fifteen years, Frank Lundy had counted fifteen 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 made Trinity's kill count much higher. Later, even more victims were discovered by the Miami Metro Homicide team.
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.
Before Arthur died, he was a man in his early 60s 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 gray 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
"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." ~ DexterArthur 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 appeared 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 inside 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. She even showed 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 teenage daughter, Rebecca, whom 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 locked closed. This was 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 pinkie 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, and 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 then act like a caring father. While he was out of town with Four Walls One Heart, he always sent her post cards, signed with "Wish you were here. Love, Daddy." However, when Arthur was frustrated with her, he called her names behind her back. He finally shut her out of his life, which devastated Christine. When Dexter told him of Christine's suicide, Arthur showed some sadness, but called her "weak."
The 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 Arthur 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 in order to have himself beaten senseless, while yelling insults at his attacker. This represented the abuse that he had endured from his own father. For his mother, he lamented the loss of her from suicide and so would force a mother of two to jump to her death. He then addressed her body as "Mommy" and briefly grieved.
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 bomb shelter. For a few days, Arthur attempted to get the boy to play with his train set, while constantly calling him "Arthur." The boy repeatedly told Arthur that his name was Scott, not Arthur. During this time, Arthur never harmed Scott but he refused to let Scott have food unless he put on pajamas 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. In Arthur's troubled mind, this would preserve the boy's innocence. However, Dexter arrived in time and rescued Scott before he died.
Arthur became very defensive when Dexter called him a pedophile, perhaps because of his pristine reputation (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. He would force the young woman into the bathtub with his unclothed self and keep her subdued with a sleeper hold. He then sliced her femoral artery with a straight razor, which led 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, likely to wash off his sins and mixed emotions.
The Forgotten Son
The next victim was always a woman of his mother's age with two children, like himself and his own sister. He would stalk women until he found the right one. To meet the woman, he would pretend to be a kind old gentleman, either walking a dog or some other mundane task, so that he could introduce himself. He easily adopted the personality of common courtesy and small talk. Soon after, he'd drop the act, get her alone, and threaten her as he ordered her to drive to a tall, abandoned building and accompany him to the top. From there, he told her to commit suicide by "letting go" (just like his mother did). He urged her to fall backward based on her own will. If she refused to comply, Arthur would threaten to make her children suffer if she did not follow his instructions. Eventually, to protect her family, the woman let herself fall and die. Arthur would then leave a smudge of Vera's ashes near her, with her hand pointing at them. While viewing he woman's body, Arthur felt a flood of emotions and called her, "Mommy."
Father Vs. Son
The fourth victim in a cycle was always an older man with two children, Arthur would locate a father matching the age of his own father. Because not every one of his victims was a drunkard, he would find someone else to take out his drunken fury on Arthur with multiple punches and kicks while Arthur shouted insults (much like his own father would do to him). After the beating, Arthur would stalk another man and yell insults at him as he was bludgeoned to death. (After a recommendation from a local store clerk, Arthur used a hammer in his latest cycle.) During this process, Arthur felt like a vulnerable man fighting back against his father, despite the fact that his victim was the one on the defense. Once again, Arthur left trace evidence of ash with the dead man pointing at it. Arthur then returned to the reality of his current life.
The True Arthur
Arthur, at times, had a hard time accepting his true self. This seemed apparent when he was faced to kill a deer and began to cower, as if he had never picked up a weapon before. This may suggest that he did not take pride in his killings. By doing what he did, Arthur attained a specific recollection of the events of his childhood and likely tried to prove how 'innocent' he was, even in such an indirect and reprehensible manner.
Arthur claimed to dislike the "demon" within himself. He contemplated ways to stop it, to kill the demon, and decided he needed to kill himself. Little to Dexter's knowledge, Arthur had built his own coffin in preparation. Thus, a planned trip was made to a Tampa dig site where Arthur could jump to his death, much like his mother. After learning from Dexter, that Dexter killed a man (although Arthur believed it to be accidental), he began sharing his past with Dexter, although he did not reveal that he kills people.
Arthur changed drastically at this point, becoming almost ecstatic about his newfound "friend" and went overboard in his interactions with him and other people. Dexter seemed to be Arthur's way of confessing to his sins without actually saying them, and happy to be free of them. Later, Dexter prepared a kill room and attempted to nab Arthur in his hotel room, but found him missing. Dexter walked to the Four Walls Build to find Arthur and was surprised to find him about to commit suicide. Ironically, Arthur's death was prevented by Dexter, when he reluctantly saved his life, just so that he could have him on his table. Arthur then acted as if new life has been breathed into him and he praised Dexter, believing that God sent him to save his life. However, Arthur soon returned to his previous personality, no longer wanting to end his own life, preferring to continue on in his bloodthirsty ways.
The true Arthur appeared when Dexter (playing as Kyle Butler) found out just how far Arthur would go in his acts of violence. After a mishap during Thanksgiving dinner, in which Dexter almost killed Arthur in his own home, Arthur started another kill cycle, earlier than expected. While stalking Arthur, Dexter observed him kidnap a young boy. 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 confronted one another, but Arthur managed to escape.
While on the hunt for who Dexter really is, Arthur was shown to be a cold and calculating man that would use bait to get 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 worked and met him face to face in the Homicide department...a true stare off occurring between the two. After a few threats, Dexter tailed Arthur to a parking 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.
Arthur took pride in his car, and had become highly infuriated with Jonah for damaging it. After taking the windshield off, he took it to a body shop to be fixed and re-painted. During this time, he acted out his revenge on Dexter for not only stopping his cycle, robbing him, and attempting to kill him earlier. He goes to Rita's house and sets her up for a kill in her bathtub by slashing her thigh and allowing her to bleed out. This was his ultimate punishment for Dexter.
After Arthur picked up his vehicle, he drove off with a smile on his face...truly feeling like he was getting away with murder. However, Dexter had secretly sabotaged his car by removing the oil cap and began following him until his car broke down. Dexter then captured him and took him to the kill site. Arthur finally realized that Dexter was a killer, not merely an extortionist. Arthur lamented that he never took pride in his killings, but he couldn't control his urges. He craved to be free of them, to be stopped, and felt that his prayers were finally answered because Dexter arrived to do it.
Arthur accepted his death as God's will, and went on to say that, "It's already over." Dexter was baffled by the statement, but concluded that Arthur was referring to his killings. However, Arthur was actually predicting that the same would happen to Dexter, knowing that he had destroyed Dexter's family life which was his means of keeping his humanity. Dexter's desire and ambition to become a good husband and father had already been 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. Dexter obliged his wishes before killing him with a hammer.
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 fourteen or fifteen at the time). At some point after Vera's death, the family moved to Miami.
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 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 he had a 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." In "Dex Takes a Holiday," Christine shoots Debra (wounding her) and Lundy (killing him), in order to protect her father. It is initially believed that Nikki Wald, one of the Vacation Murderers, did it. Eventually, Christine is caught and kills herself after confessing
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, a serial killer, has been active for three decades without being noticed except by Agent Frank Lundy, He dubbed Mitchell "The Trinity Killer" because he believed that he killed three at a time. However it later comes to light that he actuality kills four victims in every cycle ("Lost Boys"), each in a very specific fashion. The first victim is a young boy, age of ten, whom he forces to wear pajamas and buries alive in wet concrete. The second victim is a young woman whom he holds down in a bathtub, cuts the femoral artery and holds up a mirror to watch her die from bleeding out. The third victim is a mother of two kids whom by using threats to her family, coerce her to jump off a building. The fourth victim is an older man, also a parent of two children, whom he bludgeons with a hammer. (Before the last one, however, Arthur antagonizes another man to beat him up e.g. Mike.) He's immaculate, careful to never leave a trace of his presence at the scenes aside from an ash smudge. His killings recreate the traumatic deaths of his own family members ("If I Had a Hammer"). His first known cycle took place in Miami; and thirty years later ("Living the Dream"), he returned to the same locations to kill again.
In "Road Kill", Arthur reveals his back story to Dexter. When he was ten, in 1959, he walked in on his sister, Vera, showering. When she saw him, she panicked and slipped, smashing the shower door. Her femoral artery was slashed in the process. Following this, his mother, Marsha, became very depressed and committed suicide the following year by jumping to her death. His father, Henry, began drinking heavily, and was physically and verbally abusive to Arthur, blaming him for the deaths. In 1964, Henry was bludgeoned to death with a hammer in an alley (Dexter theorizes that Arthur was the killer, being fifteen at the time). In the kill cycles, the young boy victim symbolizes Arthur himself on the night of Vera's death, his last moment of innocence.
Despite Arthur's serial killing, he manages to maintain an apparently normal family life with his wife, Sally, and two children, Jonah and Rebecca. He works as a high school teacher and is a church deacon. Also, he is a leader of Four Walls One Heart, a charitable Christian home building organization, which he uses as a cover for his travels throughout the states. He keeps home building plaques as trophies for his kills. However, his happy suburban life is a facade. it's revealed in "Hungry Man" that Arthur is extremely controlling, domineering, and verbally and physically abusive to his family.to Debra.
Having just learned Dexter’s name, Arthur tells Dexter that he’s “not very good at vigilante-ism” and walks unconcerned out of the police station. Dexter speeds after Arthur to a bank parking garage, where he sedates Arthur and takes his personal belongings. The police show up and Dexter quickly hides the cash above Arthur’s van. When Dexter loses his temper at the police and other driver, he’s arrested.
While Dexter’s in jail, Arthur wakes up and discovers that he’s been robbed by Dexter. Enraged, Arthur returns home and demands his fearful family’s cash and jewelry, vowing revenge on the person who stole from him. During an online search, Arthur finds an address for “D. Morgan” but, when he breaks into the apartment, he learns that a Debra Morgan lives there. Afterward, he discovers Dexter’s true address.
The next morning, Rita and Harrison depart in a cab for the airport. Dexter immediately heads to the Mitchell house, only to be told that Arthur was gone by morning. While still there, Dexter is caught up in a police raid. During this time, Rita returns home for her forgotten I.D. and arranges a later flight. This is when Rita is murdered, according to the FBI in "Hello, Bandit."
As Dexter looks through Arthur’s wallet, he notices an invoice from a body shop and realizes that Arthur’s Mustang is there, being repaired. At some point, Arthur picks up his car and Dexter manages to remove its oil cap. He then follows Arthur in his own car until Arthur's car breaks down. Dexter captures Arthur and takes him to the fallout shelter. He realizes that Dexter is a serial killer, not an extortionist. After his kill ritual, Dexter disposes of Arthur’s dismembered body in the Gulf Stream.
Dexter returns home, only to find Rita murdered in one of Arthur’s bathtub rituals.
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 Case, 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")
Due to his life as a teacher, Arthur Mitchell's cycles began to take 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.
- Ten-year-old boy buried alive: 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.
- Young woman bleeding out in the bathtub: Represented Arthur's sister, who accidentally died while she was taking a shower. Arthur startled her and she fell, breaking the shower doors, and cutting her femoral artery.
- Middle-aged mother of two to jumps to her death: 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.
- Middle-aged father bludgeoned to death: 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.
- Christopher Kavanaugh - Live Burial (murder not shown)
- Lisa Bell - Bathtub
- Tarla Grant - Jumper
- Earl Doorman - Bludgeoning
The following victims are the few kills that Arthur made outside of his kill cycles.
- 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.
- Christine Hill - She committed suicide by shooting herself after police realized she killed Lundy, and Arthur, her father, rejected her.
- 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
- Himself - nearly committed suicide from falling, as some of his victims were forced to do ("Road Kill")
- 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 by 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.
- "Camoflauge is nature’s craftiest trick.” ~Dexter, referring to Arthur ("If I Had a Hammer")
- 100 Oceangate (bludgeoning)
- Arthur Mitchell's Childhood Home
- Arthur Mitchell's House
- Fallout Shelter (kidnapped boy)
- Four Walls One Heart
- Lisa Bell's House (bathtub murder)
- Mike (provoked beating)
- Old Port Warehouse (jumping death)
- Sacred Fellowship Church
- Trinity Case
- William Moseley High School
- The Trinity Killer has been polled by viewers 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.
- Walter Kenney aka The Tooth Fairy Killer is another older serial killer.
|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 Seven 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.
- Both Mitchell and Saxon took the life of someone Dexter cared about after he chose to spare them, when he had the opportunity to either kill them or let them die without raising suspicion (in Mitchell's case Dexter saved him from falling off a roof to his death; in Saxon's case Dexter tied him up when he could have killed him, and Saxon escaped his bindings).
- 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.