Landsman is the main source of comic relief in the series due to his laziness, girth, overeating, and penchant for reading pornographic magazines while on the job.

He has the duty of ministering in the informal "detective wakes" held in honor of the deceased at Kavanaugh's, the bar frequented by many in the department, a task he completes with uncharacteristic reverence and emotion.

Landsman's squad consists of Jimmy McNulty, Bunk Moreland, Michael Santangelo, Ray Cole, Ed Norris and Vernon Holley.

When Rawls gives Santangelo an ultimatum of clearing a "whodunit" case by day's end, Landsman sends him to a phony psychic.

When Santangelo sees that he has been given information regarding an open homicide, he thanks Landsman, who tells him that the Gypsy routine was a joke and that it had been Bunk and McNulty who saved his career.

[3] Landsman's squad handles the case of the killing of Wendell "Orlando" Blocker and wounding of Kima Greggs, and he is personally involved in the investigation.

Landsman later appears following the death of Derrick Waggoner, a black plainclothes officer accidentally killed by Prez, who had mistaken him for a criminal.

Landsman is personally angry at the death, referring to it as a "clusterfuck" as Waggoner was a 6+1⁄2-year veteran who was 16th on the current sergeant's list with two commendations while Prez is known for his incompetence and still in the department all due to his father-in-law Stan Valchek, the Southeastern district commander.

When his detective Ed Norris informs him he's investigating the murder of a state's witness Landsman passes the knowledge on to Major Valchek in secret.

Landsman then is seen delivering the eulogy for Colonel Foerester who he claimed had a miraculous career serving 39 years without a trace of bitterness or hostility, a rarity in the Baltimore Police Department.

Landsman then witnesses Detective Lester Freamon discovering dead bodies in abandoned houses and is initially against their discovery because it will raise the city's homicide rate.

When more bodies are discovered, Landsman realizes the squad can't maintain an acceptable clearance rate and becomes less concerned about the department's numbers.

After hearing that the teenager's death was accidental, Landsman decides not to press homicide charges sending him to a psychiatric unit at Bayview instead.

[5] The real Jay Landsman can also be seen on The Wire in the role of Dennis Mello, administrative aide to Major Colvin, first in an uncredited appearance in the season 2 episode "Stray Rounds", and later as a regular cast member.

The real Landsman was the inspiration for detective John Munch, a character from Homicide: Life on the Street and Law & Order: Special Victims Unit.