DURHAM, N.C. — Prosecutors are digging deep into Mike Peterson's past. They are looking at his sexual history and the death of his friend, Elizabeth Ratliff.

Eighteen years ago, Ratliff was found dead at the bottom of a stairway at her home in Germany. The prosecution believes the circumstances mirror those in Kathleen Peterson's death, and they want the jury to know all about it.

Defense attorney David Rudolf is fighting that, but he does not seem too worried. He does not think the jury will buy the prosecution's theory that Peterson killed both women.

"I think it's just so incredibly weak that it will end up weakening their case, rather than strengthening their case," Rudolf said.

Prosecutor Eric Evenson thinks otherwise.

"I would think if that evidence can be proved, it would be very powerful," he said.

Evenson succesfully prosecuted Barbara Stager in 1989. Stager shot her husband, a high school coach, with a gun he kept under his pillow. An investigation revealed Stager's previous husband died in similiar fashion 10 years earlier. That evidence helped clinch her conviction.

"We had two husbands both die at the end of a .25-caliber pistol," he said.

Evenson said for a judge to allow a previous incident in as evidence, there must be unmistakable similiarities.

"Accidents, by their very nature, are not frequent. They're unusual events," he said.

District Attorney Jim Hardin may use one of Ratliff's neighbors to link Peterson to her death. Karin Hamm said she saw Mike Peterson quickly leaving the Ratliff house the night she died. The hearing on Elizabeth Ratliff will be in two weeks.

Prosecutors also found evidence they believe points to Mike Peterson being involved in homosexual relationships, although they are not saying how it is relevant to the case.

The judge will listen to their arguments to decide if Peterson's sexual past should be admitted as evidence. A date for that hearing has not been set.