Michigan's attorney general filed charges Tuesday against a judge and a prosecutor he said worked together to allow two police officers to lie on the witness stand in a drug trial, allegations that he said "undermine the credibility of our justice system."

The police officers were charged along with retired Wayne County judge Mary Waterstone and Karen Plants, who last year left her job as an assistant prosecutor handling drug cases in Wayne County.

At the 2005 drug trial of Alexander Aceval, Plants is accused of allowing the officers, from the Detroit suburb of Inkster, to lie about their relationship with a paid informant and the informant's role in the seizure of 47 kilograms of cocaine.

Transcripts of the private talks between the judge and prosecutor helped Attorney General Mike Cox bring charges.

Plants told Waterstone that lies were necessary to protect the identity of the informant, who was a trial witness, according to a report by state investigator Michael Ondejko. Waterstone also signed an order forbidding companies from releasing the informant's cell-phone records to defense lawyers, further concealing his relationship with police, Ondejko wrote.

"It is a sad day because law enforcement professionals are involved as defendants," Cox said. "Nonetheless, this case is important because the allegations here undermine the credibility of our justice system."

Aceval's trial ended in a mistrial. He later pleaded guilty to possessing 1,000 grams or more of cocaine and won't be eligible for release from prison until 2015.

Waterstone, 69, of Detroit, is charged with four felonies, including improper communications with Plants and concealing perjured testimony. Plants, 46, of Ferndale, is charged with six crimes, including conspiracy. The police officers, Robert McArthur and Scott Rechtzigel, are charged with conspiracy and perjury.

The four defendants were released on $25,000 bond each after not guilty pleas were entered on their behalf in 36th District Court.

"These charges are obscene," Plants' attorney, Ben Gonek, said outside court. "... The defendant in the criminal case was a piece of garbage who was dealing poison in our community."

Waterstone and her three lawyers and the officers' lawyers had no comment after the arraignment. The next court date is April 28.

Plants' former boss, Wayne County Prosecutor Kym Worthy, declined interview requests and issued a brief statement: "Our system of justice is based upon the presumption of innocence and the right to a fair trial. I sincerely hope that these defendants will be afforded the same rights as others."

Aceval's lawyer, David Moffitt, has tried to get his client's 2006 guilty plea thrown out, arguing that perjury at the 2005 trial should have erased the case forever.

On Feb. 5, the Michigan Court of Appeals said the conduct of Waterstone and Plants was "disgraceful," but it ruled against Aceval, noting that his trial had ended in a mistrial. Aceval is appealing to the state Supreme Court.

Moffitt was in court Tuesday for the arraignment of the former judge and ex-prosecutor.

"No one can be pleased about public corruption. On the other hand, a strong message needs to be sent that no one is above the law," he said.

The Michigan Attorney Grievance Commission last year filed a complaint against Plants. It is pending at the state Attorney Discipline Board. No complaint is pending against Waterstone.