In Walker's case, veteran defense lawyer Gregory Pagano said the allegations against the officer would likely imperil hundreds of drug cases.
Three years ago, he said, one of his clients accused Walker of conduct that mirrored the accusations the FBI lodged against the officer this week.
After Walker arrested him on drug charges, Joseph C. Newton and his girlfriend told Pagano that Walker had stolen the keys to their homes and burglarized both.
"I doubt that these are the only times that this happened," Pagano said. He said he planned to appeal Newton's arrest, citing the officer's alleged conduct.
Pagano said Walker was the only officer involved in the arrest of Newton, who pleaded guilty and is serving an 18-to-36-month sentence on drug-dealing charges.
Defense lawyer Fortunato N. Perri Jr., who has represented at least seven defendants Walker had arrested on drug charges since 2010, said he was "evaluating all the cases in which this officer was involved."
Another defense lawyer, Eugene P. Tinari, predicted prosecutors would quickly drop charges against his client, Jahlil French, as well as three codefendants Walker arrested on drug charges last year.
"Given what Officer Walker is alleged to have done, it's impossible for them to go forward," he said.
Tinari predicted that lawyers across the city would take similar action and that the effect would be widespread because Walker is one of the busiest officers on the force.
"It's unbelievable," Tinari said. "He's a mainstay of the courthouse."
Tinari's father, Nino, said he would file motions to have convictions overturned in cases in which Walker arrested his clients.
"He went the route of the people he was arresting," said the elder Tinari, who is also working to overturn convictions involving the six narcotics officers who were transferred from the narcotics unit this year.
In the 285 cases involving those six officers, District Attorney Seth Williams has said he would not use any of them as witnesses. As for cases that had already resulted in convictions, Williams has said the courts should determine whether any of those cases should be reversed. In several cases, judges have granted defendants the right to new trials, and prosecutors have withdrawn the charges.
The courts are likely to see a flood of similar challenges to drug convictions and pending drug cases over the next two months. By law, petitions for new trials must be filed within 60 days after new evidence is discovered.
Scores of such petitions were filed in the first two months after the news broke about the investigation of the six other officers, who now are serving in lower-profile jobs in the department.
Public defender Bradley S. Bridge, whose office has handled more than 100 of Walker's cases since 2010, said he expected the District Attorney's Office to withdraw prosecution in all of Walker's cases that had not yet gone to trial.
In cases involving earlier convictions, he said his office would quickly file petitions with the courts for new trials.
Contact Mark Fazlollah
at 215-854-5831 or firstname.lastname@example.org.