ALBUQUERQUE, N.M. - David Young started out working for the city in fleet maintenance. He ended up prowling Albuquerque's streets, arresting prostitutes and their clients for the police department's Special Investigations Division.

At no time, however, was Young a sworn police officer. A civilian employee of the department for 10 years, he worked as a volunteer reserve officer when he made his arrests. Under New Mexico law, arresting officers handle misdemeanor prosecutions in metropolitan court. Young appeared as the prosecuting agent in several cases.

Since news of Young's role surfaced in late August, the criminal justice system here has been thrown in turmoil. One prostitution case that he handled was dismissed before it went to trial, and defense attorneys are preparing to appeal nearly a dozen more.

The police department has suspended its reserve program and identified 46 other criminal cases that reserve officers handled, ranging from traffic tickets to domestic violence. Those other cases may also be challenged in court.

"It's pretty wild," said Mary Han, a civil rights attorney the public defender's office tapped to handle the cases involving Young. "If you or I were to go out and impersonate a police officer, we'd go to jail. ... It's a real perversion of the legal system."

Police officials say Young was acting with the blessing of the department -- and always with sworn officers close by.

"This will end up being an attorney discussion and a ruling by attorneys," said police spokesman John Walsh, who described the issues involved as "technicalities."

The key question: What makes someone a cop?

Young, who has not been accused of wrongdoing, has retained an attorney who said that, like all of the department's 63 reserves, Young spent time at the local police academy -- more than 700 hours -- learning investigative procedure and other staples of law enforcement.

The attorney, John D'Amato, added that, like full-time police officers, Young goes to the firing range every month to remain qualified to carry a firearm.

D'Amato called his client, who is employed by the department to help police set up electronic surveillance equipment, "more trained and certified in more areas than most police officers are."

He joined the reserves six years ago.

New Mexico law repeatedly identifies police officers as "salaried" law enforcement personnel. But Albuquerque police cite one provision that allows a chief to deputize any individual as his agent, saying the law could permit someone such as Young to legally act as a fully sworn officer.

Although state law does not allow reserve officers to make arrests in traffic stops, they are allowed to make other arrests.

But since 2007, it has been required that reserve officers be accompanied at all times by a sworn police officer. Back then a top Albuquerque police official warned reserves in the vice unit that they should not be acting alone. Young arrested 24 people after that warning, although police say he was under supervision.

The Albuquerque Journal, which broke the story, reported that Young was paid overtime during the arrests. Walsh said the payments might have been for his civilian-side job setting up surveillance.

Police say they tapped Young to work undercover because the vice unit needs a supply of fresh faces to catch prostitutes and their clients. All undercover operations are by their nature tightly supervised, Walsh said. On his police reports, however, Young lists only himself as the arresting officer and does not list an assisting officer.

In many reports and complaints he filed with the court, Young also identifies himself as a police officer or detective. In a handful, he lists himself as a reserve officer. He is also listed as the contact for defendants who wish to delay their court appearance.

Han said Young negotiated plea deals in court and occasionally warned defendants about the sentences they could face if they did not admit to their crimes.

Han also noted that in several of Young's arrests, there is no record of the alleged prostitute asking for money for sex, the probable cause that would be required to prosecute the case.

In the case that was dismissed in August, for example, Young wrote that he drove up to a 45-year-old woman standing at a "high-prostitution area." She asked him if he was a cop and challenged him to touch her breast to prove he was not.

According to court records, Young did touch her. She then asked him to expose himself.

"I did not expose myself and she did not say anything anymore," Young wrote. "She was then taken into custody without incident."

Young's activity has become an issue in mayoral race. In October incumbent Mayor Martin Chavez faces two challengers who are hammering him on public safety.

"It is a taxpayer nightmare," said Tim McGiven, spokesman for challenger Richard Romero, referring to the city's liability from lawsuits by those Young arrested. "We can't just say it's going to be solved in the courts. There's got to be accountability in the force."

But the mayor's office has been dismissive of such complaints, saying the case is overblown. Scoffing at the challenges to Young's arrests in court, top aide Pete Dinelli told the Journal: "The public defender has conveniently overlooked the fact that these people have been convicted of these charges."

Police have said they expect to reinstate the reserve program shortly and D'Amato, Young's attorney, contended the whole case is colored by politics.

"It's a very dramatic step," D'Amato said of the suspension of the reserve program, "but it's a very dramatic time of the year. Had this happened in the spring of 2010 or the winter of 2010 it would not have been an issue."