By Tony Hanson

PHILADELPHIA (CBS) — The Philadelphia district attorney’s office today announced that it is dismissing nearly a dozen additional cases linked to a corrupt Philadelphia cop, bringing the total of convictions overturned to about 85.

And additional cases are under review after officer Jeffrey Walker pleaded guilty in federal court earlier this week.

Authorities have been reviewing his cases since his indictment last May. In this latest group, 11 convictions have been overturned and dismissed.

Some involve defendants still in prison. Assistant public defender Bradley Bridge says he is already taking steps for their release. He says Walker’s significant role in all these cases undermines the convictions.

“What this means is there is no way to really know what happened,” Bridge tells KYW Newsradio. “The prosecutor’s office has appropriately concluded that they cannot rely on anything Officer Walker has said because he has been established to be a perjurer, a man who plants drugs, and as a consequence we don’t know whether the people involved are guilty or not guilty, but we know their convictions can not justly stand. ”

Officer Jeffrey Walker was caught in an FBI sting last May (see related story). He pleaded guilty to corruption and related crimes (related story).

Authorities say other Walker cases were reviewed but, because he played a lesser role or there is other corroborating evidence, those convictions will stand.