A man imprisoned for killing an off-duty Cook County Jail officer is seeking to have his conviction thrown out, claiming in court papers that his attorney failed to pursue leads that another man committed the murder because the lawyer also represented that potential suspect.

Bernard Mims, now 33, was convicted of murder and attempted murder in 2006 and is serving a sentence of 90 years in prison.

In papers filed May 20 in Cook County Circuit Court, Mims' new lawyer alleges that attorney Daniel Franks had a conflict of interest when he simultaneously defended Mims as well as a man who Chicago police suspected might have been involved in the jail officer's murder.

Franks' failure to investigate his other client, as well as two other men potentially involved in the killing, "plainly prejudiced" Mims, lawyer Kathleen Zellner, who now represents Mims, wrote in asking a judge to dismiss Mims' conviction. If Franks had pursued the leads at trial, Zellner said, there was "a reasonable probability" that Mims would not have been convicted.

"You can't jeopardize one client to protect another client," Zellner said in an interview.

Franks, a veteran criminal defense attorney, declined to talk on the record for this story but in a statement staunchly defended his work, saying trial strategy dictated his handling of the case. Introducing evidence against other potential suspects could have backfired against Mims by bringing attention to his gang background, he said.

A transcript of the trial shows Franks put up a spirited defense for Mims, aggressively attacking prosecution evidence and emphasizing that Mims had been shot days before the murder and was still recuperating from his injuries.

Legal experts, however, said Franks may have had an ethical duty to notify the judge of the potential conflict and withdraw as Mims' attorney. Trial strategy didn't need to factor into the decision, they said.

At issue is a bedrock principle of the attorney-client relationship: the loyalty and independent judgment a lawyer owes his client. A lawyer can't fairly represent two clients who are both potential suspects in the same crime because their interests clash, according to legal experts.

"You're supposed to be a zealous advocate, not a halfway advocate," said Clifford Scott-Rudnick, who teaches professional responsibility at John Marshall Law School in Chicago. "So if something is going to compromise that, then you should get out of the case."

The Cook County state's attorney's office stands by the conviction of Mims and is fighting his appeal. But spokeswoman Sally Daly said prosecutors were not aware of Franks' alleged conflict of interest at the time of the trial. As a result, the office has referred the matter to its unit that examines wrongful conviction claims to do "a full review" of the potential conflict.

The office will also look into whether Franks' other client at the time was involved in the shooting. At the time of Mims' trial, the assistant state's attorneys who prosecuted the case did not find the evidence against that person credible, Daly said.

"We would not call the case flawed at this time, but we are going to take a closer look," she said.

The Tribune is not naming the other potential suspect because he has not been charged in connection with the murder. The man, who is awaiting trial on an unrelated felony weapons charge, declined to comment through his current attorney, Dawn Projansky.

Mims was arrested nearly four years after the murder of off-duty correctional Officer Dwayne Baker outside a South Side apartment building in October 2000. Two suspects had stepped from an SUV at a gas station across the street and opened fire with an assault-style weapon.

Police and prosecutors theorized that rival gangs were battling over drug sales at the Michigan Boulevard Garden Apartments at East 47th Street and South Michigan Avenue. Baker, who was moonlighting as a security guard at the building, was fatally shot, but two other off-duty correctional officers working with him escaped injury.

Before Mims' trial, prosecutors turned over to Franks affidavits from 2001 in which two Chicago police detectives documented their investigations into gangs, drugs and slayings as part of an effort to win court approval to secretly record calls. According to the affidavits, the detectives had developed information pointing to other suspects in Baker's murder and expected the wiretaps to capture conversations about the murder that would include Franks' other client in the discussions.

However, that man was not recorded on the wiretaps nor was his name mentioned, according to the state's attorney's office. In addition, prosecutors do not recall any witnesses bringing up his name during the investigation, Daly said.

Court records confirm that Franks' representation of both clients overlapped. He defended the one man in a drug case from April 2000 until his guilty plea in October 2004 as well as in a separate gun case from November 2005 until October 2006. Franks represented Mims on the murder charge from shortly after his arrest in August 2004 until shortly after his sentencing in July 2006. In addition, Franks had defended the other man against an earlier murder charge. .

During Mims' trial, prosecutors built their case around the testimony of two eyewitnesses who belatedly identified him. Franks attacked their credibility, noted that no physical evidence tied Mims to the shooting and stressed how Mims was still laid up at the time of the murder after being shot in the groin area 10 days earlier.

The mother of Mims' five children testified that Mims was essentially bedridden and never left home for several weeks after the shooting. Prosecutors challenged the alibi, saying the woman was biased in Mims' favor and that his wounds did not leave him housebound.

Circuit Judge Michael Toomin, who heard the evidence instead of a jury, convicted Mims of murder and attempted murder.

After the verdict, Franks made an impassioned plea for a new trial, calling the evidence weak. One of the prosecutors, Rob Robertson, now in private practice, recalled recently how strenuously Franks challenged Toomin over the verdict, even questioning the veteran judge's understanding of the evidence. At sentencing Franks suggested that the judge convicted Mims on weak evidence because of the murder victim's law enforcement background.

In his statement to the Tribune, Franks insisted his strategy at trial was sound and that using some of the information turned over by prosecutors could have backfired on Mims, who was a gang member.