Bennie Starks

Bennie Starks was convicted of the 1986 sexual assault of a 68-year-old Waukegan woman, but he was awarded a new trial in 2006 after DNA tests excluded him as the source of semen on the victim. That trial is tentatively set to take place next year. Lake County prosecutor Michael Mermel plans to use the victim's identification of Starks as her attacker. (Tribune photo by Chris Walker / December 4, 2008)

DNA evidence has been widely embraced over the last two decades as a powerful forensic tool to prove a defendant's guilt or innocence. But in Lake County, authorities have sometimes pressed for convictions even when the DNA doesn't match a suspect.

Consider three active cases overseen by Michael Mermel, chief of the criminal division for the Lake County state's attorney's office:

When DNA evidence excluded a man convicted in the rape and battery of a 68-year-old woman, Mermel suggested the victim had consensual sex with someone else.

When DNA evidence excluded a man in the rape and murder of an 11-year-old girl, Mermel and another prosecutor suggested that the girl may have been sexually active. The DNA, he said, was a "red herring."

And, just recently, when lawyers for the man charged in the killing of his 8-year-old daughter and her 9-year-old friend said in court that DNA evidence from semen excluded him as the perpetrator, the Lake prosecutor had another explanation.

Mermel said DNA may have gotten inside the 8-year-old's body as she played in the woods at what became the crime scene—a place where Mermel said some couples go to have sex. The girl was found fully clothed.

In each of the cases, all likely to go to trial in the new year, Mermel argues that other evidence, mainly confessions and witness identification, carry greater sway than the genetic material.

That attitude startles some DNA experts and others in the criminal justice system.

"The vast majority of prosecutors in the United States generally are willing to walk away from a case where DNA excludes a suspect," said Joshua Marquis, an Oregon prosecutor and member of the board of directors of the National District Attorneys Association.

'Forensically significant'

In these Lake County cases, several DNA scientists and others say the prosecutor's explanations are difficult to imagine.

"It's just amazing how convincing DNA can be if it supports your case and how unconvincing it is when it doesn't support your case," said William Thompson, a lawyer and DNA expert at the University of California at Irvine.

Defending his office's approach, Mermel said Lake prosecutors believe in DNA "when it is forensically significant."

"If we thought the evidence excluded the defendant in any of these cases," he said, "we'd dismiss them."

Mermel pointed to another rape case where his office supported vacating a man's conviction after DNA excluded him as the source of semen in the victim.

But in that case the defendant had served his prison sentence and been released.

'DNA ought to humble us'

At a hearing six years ago in the case of Bennie Starks, who had been convicted of raping a 68-year-old woman, Mermel made an intriguing vow.

Though a semen stain on the victim's underwear contained a genetic profile different from Starks' DNA, Mermel said it was not enough to prove his innocence. What would help Starks' claim, Mermel said, was if the semen came from inside the woman's body.