The lawyer for a skinhead charged with killing an African American man in a 1989 "racial murder" hammered yesterday at the credibility of a key prosecution witness: a former girlfriend of the accused who the defense contends is lying out of spite.

Under intense cross-examination by defense attorney J. Michael Farrell, Patricia Miller conceded that she had been on medication Tuesday, when she provided damaging testimony against her former boyfriend Thomas Gibison, 35, of Newark, Del.

She also confirmed that she once was a cocaine user and had been in and out of clinics and hospitals at least 10 times.

Farrell also got the woman to talk about her relationship with Gibison, and the steamy letters and photos she sent him while he was incarcerated.

"You're my forever," she wrote in one letter. "I now know that to live without you is not to live at all."

Miller, who said Gibison admired her because she was "so Aryan," wrote in one letter, "I want to be your wife, to be the mother of your child."

All that changed, Farrell contends, when Miller discovered that Gibison had married someone else.

On Wednesday, Miller testified that Gibison had told her that he killed Aaron Wood, 35, an African American, because he wanted prove that he was a committed white supremacist.

Wood, who lived in North Philadelphia, was gunned down near Girard College on April 16, 1989.

Farrell contends that his client is innocent and that Wood's slaying was the result of an unpaid drug debt.

The killing remained a "cold case" for 19 years until Miller, who lives in Delaware, tipped off federal authorities about Gibison's possible connection.

At one point, Miller, appearing exasperated with the questioning, said she wrote the letters because she was afraid of Gibison.

"I'd say anything to keep him happy and content," she said. She said she fed him "sick fantasies" in an attempt to keep her family and herself alive.

"I'm not getting back at Tom," she said. "He is going to get what he deserves."

Also yesterday, Miller continued to give the jury - which includes six African Americans - a tour of the world of white-supremacist skinheads.

According to Miller, Gibison's spider-web tattoo "was a status symbol" indicating that he "had killed a black person.

The killing, she said, "meant nothing more to him than killing a fly."

She added that if Gibison had killed more African Americans he would have been "entitled" to add a red teardrop tattoo within the spiderweb for each victim. He does not have any red teardrop tattoos in the spiderweb.

Farrell has said that his client is simply a "blue-collar skinhead," not a racist or white supremacist.

Trial resumes today before Common Pleas Court Judge M. Teresa Sarmina.