Prez married the daughter of Southeastern District Commander Stanislaus Valchek. He served for three years in the the Auto Theft Unit until he discharged his firearm into his squad car in a panic. He filed a false report and claimed he was being fired upon until the ballistics matched the discharged bullets to his service weapon. The Baltimore City State's Attorney's Office intended to indict Prez for false report but Valchek ensured he was reassigned to casualty section under Lieutenant Cantrell.
Prez is sent to Lieutenant Daniels' Barksdale detail because Deputy Commissioner Burrell tells the unit commanders to dump their most incompetent officers on Daniels. Upon arrival at the detail, he accidentally shoots a wall while showing off modifications to his gun. Daniels is appalled, but agrees to keep Prez if Cantrell will also give him Leander Sydnor, a highly-respected detective.
Later, Prez, Herc, and Carver drunkenly incite a near-riot in the Barksdale towers. They arrive in the middle of the night, drunk, and begin harassing people; in the process, Prez pistol-whips a teenager with his service weapon, blinding him in one eye. Daniels stands up for his detective and protects him from serious repercussions by making up a story for Prez to tell I.I.D. (Internal Investigation Division); Prez is ultimately suspended from street duty, but Valchek is pleased with Daniels for helping Prez.
Stuck in the office, Prez grows bored and begins playing with the pager codes the Barksdale crew uses, eventually breaking them and making a major contribution to the case. Under Freamon's mentoring, he discovers a facility for wiretap work and for chasing the paper trail, eventually becoming a valuable member of the team.
Prez confesses to his father-in-law that his earlier problems had largely been due to dissatisfaction with his traffic police work. He told him that detailed case work had become his passion and that he wanted to continue to work major cases. When Valchek starts feuding with Frank Sobotka, he requests a detail similar to the previous Barksdale detail. Instead, Burrell gives him incompetent "humps". Prez is given minor authority within the detail, but Lieutenant Grayson will not follow his recommendations on how to proceed. Prez tells his father-in-law that the detail is making little progress, and Valchek, after seeing the unit at work, demands that Daniels become the unit commander, threatening to derail Burrell's quest to be police commissioner.
When the focus of the investigation shifts away from Sobotka, Valchek angrily confronts the detail, and berating Prez specifically. Prez stands up for their work and punches Valchek. With Prez facing charges of assaulting a commanding officer and insubordination, Daniels stands up for him a second time, pointing out that, if there is an official inqury, the FBI agents present during the incident would affirm that Prez hit Valchek only after the latter had shoved and cursed at him. Valchek agrees that Prez can return to the detail following a written letter of apology and two months of working the midnight shift as a narcotics detective in his district. 
Prez joins Daniels' newly formed Major Crimes Unit. When responding to a distress call, Prez fatally shoots a plain clothes officer, Waggoner, in a case of night-time mistaken identity. He is brought up on administrative charges and suspended because the officer was African American and the shooting was potentially racially motivated. Prez vehemently denies being racist but, due to the press and Baltimore's majority African American population, the story leaks out and prompts a hearing from both the courts and the vanguard (Baltimore's African American police officer union). Prez is shocked at the fact that he killed another officer and quits the force though Daniels, Caroline Massey and Lester Freamon (all African-American) agree to testify that he did not kill Waggoner out of racial prejudice.
Prez starts a new career as a math teacher at Edward Tilghman Middle School. As a teacher, he becomes attached to the students in his classroom, even going as far as to assist a neglected student Duquan "Dukie" Weems with laundry and food that his family does not provide for him. Prez sees through the school system's flaws, but adapts well, and becomes a decent teacher that enjoys helping the students advance through class.
By then Prez has become a well-respected teacher and has grown a full beard. Dukie Weems approaches Prez when his former teacher is leaving for the day, asking him for money for rent and to enroll in a GED program. However, Dukie's actual motive is to buy drugs to feed a new drug addiction. Prez even drives Dukie to the location Dukie claims is his home, but Prez, before driving off, sees Dukie buying heroin. Prez leaves, obviously disappointed. ("-30-")
|"The Target"||"The Detail"||"The Buys"||"Old Cases"||"The Pager"|
|"The Wire"||"One Arrest"||"Lessons"||"Game Day"||"The Cost"|
|"The Hunt"||"Cleaning Up"||"Sentencing"|
|"Ebb Tide"||"Collateral Damage"||"Hot Shots"||"Hard Cases"||"Undertow"|
|"All Prologue"||"Backwash"||"Duck and Cover"||"Stray Rounds"||"Storm Warnings"|
|"Bad Dreams"||"Port in a Storm"|
|"Time after Time"||"All Due Respect"||"Dead Soldiers"||"Amsterdam"||"Straight and True"|
|"Homecoming"||"Back Burners"||"Moral Midgetry"||"Slapstick"||"Reformation"|
|"Middle Ground"||"Mission Accomplished"|
|"Boys of Summer"||"Soft Eyes"||"Home Rooms"||"Refugees"||"Alliances"|
|"Margin of Error"||"Unto Others"||"Corner Boys"||"Know Your Place"||"Misgivings"|
|"A New Day"||"That's Got His Own"||"Final Grades"|
|"More with Less"||"Unconfirmed Reports"||"Not for Attribution"||"Transitions"||"React Quotes"|
|"The Dickensian Aspect"||"Took"||"Clarifications"||"Late Editions"||"-30-"|
- The only police officer who, throughout the series, fires his weapon or kills someone. This is representative of how little police officers in real life use their weapons in the line of duty, with many career officers never firing a single shot in the field.
- The character's code breaking facility, and the pager code itself from season one, are based on the Melvin "Chin" Farmer case investigated by Harry Edgerton and Ed Burns. His experiences as a teacher are based on those of Ed Burns, who retired from the police to become a teacher in Baltimore.
- Dan Kois (2004). Everything you were afraid to ask about "The Wire". Salon.com. Retrieved on 2006-07-12.
- Alvarez, Rafael (2004). The Wire: Truth Be Told. New York: Pocket Books.