OAKLAND -- By the time Marcel Perry took the witness stand in his own defense earlier this year to deny he shot and killed a rival gang member, the case against him had already been made.

A few days before in a dimly lit courtroom, illuminated by only a video playing on a flat-screen television, the jury watched as the then-20 year old told an entirely different story to an Oakland police homicide detective.

As if they were in the interrogation room themselves, members of the jury watched as then-Sgt. Gus Galindo shrewdly questioned Perry, starting with a friendly banter and finishing, about five hours later, with an emotional challenge to the gang member to prove that he wasn't simply a wasted, coldblooded human being.

"I wake up every day, every hour, every minute. What the (expletive), man? Why did I put myself in this position? What was I thinking?" a teary-eyed Perry said. "It's real stupid, man. There ain't no way out of it."

It was a pivotal moment in the case as it showed Perry voluntarily confessing to the murder without being coerced. The jury witnessed the entire interrogation, slamming the door on any defense that Perry was somehow tricked into giving a false confession.

Just three years ago, such a piece of evidence would have never made its way before a jury because it would not have existed.

Under pressure from the Alameda County Public Defender's Office and after questions were raised about how it conducted its investigation in the killing of journalist Chauncey Bailey, the Oakland Police Department finally relented and began videotaping its interrogation of suspects.

Those videos are now making their way before juries, giving prosecutors another vital tool and taking away a common defense tactic of raising doubts about the police department's interrogation methods.

"There are no issues as to what went on," said deputy district attorney Patrick Moriarty, who successfully tried the murder case against Perry. "The defense attorney cannot make the argument that we are missing something."

That wasn't always the case.

Until roughly late 2008, the Oakland Police Department was one of a few law enforcement agencies in the Bay Area that did not record questioning of suspects.

Instead, detectives would take notes and only make an audio recording of a statement after a suspect confessed to a crime. Once a confession was made, detectives would turn on the recorder and ask a suspect to repeat the confession.

That method left room for defense attorneys to raise doubts about how and why a suspect confessed to a crime. And, it allowed suspects to claim they were fooled into giving a confession.

"That raised just enormous questions for us as to what was going on," said assistant public defender Ray Keller. "Clients were giving us versions of events with allegations of misconduct. The Oakland Police Department had no way to rebut that other than saying 'we didn't do anything wrong' and leaving it up to a jury to decide."

And in some cases, Keller said, the jury did not believe the police.

"We had lawyers in the Public Defender's Office that got acquittals because of that," Keller said. "Now, if there is a question about the interrogation, it has to be based in fact. Their interrogation practices are now more transparent and reliable and less impeachable and that is good for the criminal justice system."

The video recording of interrogations has also not appeared to have impacted the willingness of suspects to confess their crimes, as the Oakland Police Department cautioned it would when officials defended past practice of not recording interviews, both prosecutors and defense attorneys said.

In fact, some said that the department's past practice of placing an audio recorder in front of a suspect was more intrusive since the current video recording equipment is virtually hidden from suspects. Cameras recording the interrogation hang from the corner of the ceiling in interrogation rooms.

"In fact, in many cases, it is extremely damaging to our clients," Keller said. "I know that not all of my colleagues think it is a great thing."

Officer Holly Joshi, a spokeswoman for the police department, said the video recordings are useful both for prosecutors to use at trials and for investigators who sometimes review the recordings to pick up clues they didn't notice during the initial interrogation.

"It's good to have a complete, accurate picture of what is going on. You can see and catch things that you might not have noticed before," she said.

Video recording equipment is in place in almost every interrogation room at the police department, Joshi said, including those in the department's homicide, criminal investigation and youth and family services units. The cameras, which cost about $20,000, begin recording as soon as a suspect enters a room, she said.

Joshi acknowledged there were some concerns about the video recordings hampering investigations by persuading suspects into not talking, but, she said investigators have realized that suspects do not notice the camera once questioning begins.

With the cameras in place for about two years now, Joshi said investigators and the department are glad a recording is taking place.

"Any tool that allows for more transparency, so people can actually see what we are really doing, those tools are in our best interest," she said. "The recordings usually end up helping us."

For prosecutors, the videotaped interrogations not only end speculation of nefarious police tactics but also provide dramatic evidence during a trial that helps prove their cases.

"Notes aren't the same as a video recording," said deputy district attorney Tim Wellman, who recently played in court the interrogation of Dajuan Flemming, a 20-year-old found guilty of murder during a drive-by shooting. "It provides an additional level of evidence."

Through the video recordings, juries can see the body language of a suspect during questioning and analyze for themselves if the suspect is being truthful. It's also easier for a jury to pay attention to a video than a garbled audio recording, prosecutors said.

"You can see the body language, you can see it changing. You would not be able to tell that on an audio tape," Moriarty said. "It's easier for a jury to watch than to just listen. It's very powerful."