His narcotics squad framed people with perjured testimony and bogus warrants and ultimately became a unit of thieves, stealing more than $1 million from drug dealers, former Philadelphia Police Officer Jeffrey Walker testified Thursday in his new role as witness for the wrongly arrested.

In a highly unusual public deposition in a federal courtroom, Walker was a key witness for scores of former suspects arrested by Walker's unit who are now seeking restitution from the city.

"Whether you believe it or not, it's true," Walker told seven plaintiffs' lawyers and a bevy of attorneys representing the city and six current and former police officers who are being sued in more than 100 cases dating back to 2012.

Walker has said he feared for his safety, and U.S. District Judge Paul S. Diamond allowed his courtroom to be used as a secure site for the deposition, continuing Friday. The seven plaintiffs' lawyers represent what Diamond has designated as "bellwether cases," the leadoff batters for the larger group of suits. The city recently settled the first of the bellwether cases for $625,000.

Walker pleaded guilty in 2014 to federal corruption charges after he was caught stealing money in an FBI string. He then testified as a government witness against his six colleagues at trial in May 2015.

The six officers - Thomas Liciardello, Brian Reynolds, Michael Spicer, Perry Betts, Linwood Norman, and John Speiser - all were acquitted.

Walker was sentenced to 42 months in prison. The six officers were given their badges back after their acquittals.

With the exception of Betts, who has retired, all the acquitted officers attended the first day of Walker's deposition as spectators. Four were in uniform.

Much of the information Walker discussed in front of his former colleagues was a repeat of his testimony in last year's criminal trial.

As in the criminal trial, Walker said he and Norman stole three kilos of cocaine from one dealer. Walker said he eventually got $17,000 for his share of the dope.

Norman declined to comment about Walker's statements, as did the other officers who attended the first day of the deposition.

The lawyers for the city and police said they could not make any comment because the lawsuit litigation was ongoing.

But one of the defense attorneys from the officers' criminal trial lashed out at Walker when told about the deposition.

"In my opinion, Jeffrey Walker has proven himself to be a liar, a thief, and disgrace to the badge," said Michael J. Diamondstein, who defended Officer John Speiser. "His testimony was worthless."

During the deposition, Walker minutely dissected search warrants and other paperwork the plaintiffs' lawyers presented to him. In one case, he said, that based on the paperwork, the suspect had been wrongly convicted.

So far, the city's District Attorney's Office and the courts have agreed to dismiss charges against some 700 suspects who were arrested by Walker and the six others.

After their criminal charges were dismissed, many of those individuals sued the city. Legal experts say those lawsuits are likely to drag on for years.