He's a reclusive, paranoid man who keeps detailed notes of whatever draws his attention as he peers out of his windows. He often calls the police for minuscule issues, even once calling them because of the way the clouds looked.
Lenny lived next to Anthony Rodrigo and was suspicious of his activities. One night, Lenny unknowingly witnessed Dexter Morgan carrying an unconscious Rodrigo to a car in preparation for his murder. Even though Lenny thought that it just was a friend helping a drunken Rodrigo, he recorded the car's license plate number.
During the Bay Harbor Butcher Case, Officer Debra Morgan and Detective Angel Batista questioned Lenny about Rodrigo. Lenny had kept all his boxes of notes through the years and he gave them the ones for 2002 (the year that Rodrigo went missing).
Debra and Angel went through Lenny's notes, laughing at some of them, until they made a discovery. The car that Rodrigo was seen taken away in had belonged to a drug dealer named Charlie Lewis. At first, they thought that Lewis had murdered Rodrigo until they noticed he had been in prison and his car was impounded by the Miami Police Dept. They realized, to their dismay, that one of their co-workers had used the car to abduct Rodrigo. Unfortunately, there was no longer a record of who had borrowed the car that night.