A day after the trial judge in the prosecution of Pennsylvania Attorney General Kathleen G. Kane warned against any retaliation against witnesses, her top deputy - the incoming acting attorney general - said he was pondering arresting a key witness against her who had an immunity deal.

Bruce L. Castor Jr., who takes over the agency after Kane's resignation takes effect Wednesday, stopped short of saying he would charge Joshua Morrow, who admitted on the witness stand that he lied repeatedly in grand jury testimony "to protect Kathleen."

But Castor, a political rival of the district attorney who prosecuted Kane, said Tuesday that he did not think the immunity order would block prosecution of Morrow on charges of lying to a grand jury.

After recanting that testimony, Morrow delivered a devastating narrative, contending that he and Kane conspired to tell a false story about their own illegal actions and to frame a former Kane aide.

A jury on Monday convicted Kane on all counts, finding that she unlawfully leaked investigative documents to the Daily News in order to damage a critic's reputation. The jury also found that she had lied to a grand jury investigating the leak. Morrow was one of the couriers who got the documents to the Daily News.

After the verdict, Montgomery County Judge Wendy Demchick-Alloy warned, "There is to be absolutely no retaliation against any witness in this case . . . directly or indirectly."

Castor, who was hired and then promoted by Kane, told reporters the judge's caution was not directed at him. "It was issued to Attorney General Kane," he said.

He added: "I'm not going to retaliate against anyone."

Castor then got off a shot at a political enemy, Kevin R. Steele, the Montgomery County district attorney who led the Kane prosecution - and who last fall defeated Castor, a Republican, in a contentious race for district attorney.

"What I can't understand is how the district attorney of Montgomery County has authority to allow, effectively allow, a person to lie before a statewide investigative grand jury," Castor said.

Steele's spokeswoman, Kate Delano, would not comment Tuesday. Neither would Catherine M. Recker, Morrow's lawyer.

Morrow, a veteran political operative who served as Kane's communications director during the election campaign leading to her 2012 victory, admitted that he served as a courier, passing the investigative material to a reporter to plant a negative story against an enemy of Kane's.

Prosecutors have said he committed no crime in serving as a courier. His legal exposure stemmed from his lies.

He made no bones about his statements. "The reality is, I lied in a grand jury," Morrow told jurors.

Steele granted Morrow "use" immunity, which means his testimony cannot be used in any action against him.

But Castor said such immunity does not bar prosecution of Morrow on perjury charges if the evidence can be assembled without using his testimony.

This is not the first time Castor, a former Montgomery County district attorney, has poked into a Steele investigation.

In the Bill Cosby case, Castor said sexual-assault charges should be dropped because he made an oral "non-prosecution agreement" with Cosby's lawyer a decade ago.

A judge shot down that argument after hearing Castor testify in February, in the same courtroom where Kane went to trial.

When Kane was under investigation, she was put under a series of court orders banning retaliation against witnesses.

Kane nonetheless fired the chief of her appeals unit shortly after a newspaper reported that he had testified against her before a grand jury. She demanded that a top agent resign after he, too, testified before the grand jury, according to a pending lawsuit. The agent has been on leave since.

She also dismissed a top human-relations official after he recommended that her chief of staff be fired over sexual-harassment complaints. In July, her agency agreed to pay $150,000 to settle a lawsuit filed by the former official.

During her trial, another former top aide, Bruce Beemer, testified that Kane once threatened she would carry out mass firings if arrested.

"If I get taken out of here in handcuffs, what do you think my last act would be?" Kane told him, Beemer said.

cmccoy@phillynews.com

215-854-4821 @CraigRMcCoy

Staff writer Angela Couloumbis contributed to this article.