In grand jury testimony last year, witness Constance Trimble said it was Reed who told her to make a fake emergency call to the police. The call lured the 27-year-old Sackett to the place where a sniper shot and killed him.
But on the stand Wednesday, Trimble was vague, and contradicted her earlier statements about the night of Sackett's shooting.
Trimble is one of Ronald Reed's former girlfriends and they have a child together.
On May 22, 1970, Trimble placed an emergency call requesting a squad car be sent to a home in St. Paul. She said her sister was in labor there and needed help. She told the dispatcher her name was Brown and that she was calling from a phone booth.
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Police investigators tracked Trimble down soon after the shooting and charged her with Sackett's murder. She was acquitted in 1972.
For years, Trimble refused to say who asked her to make the call. She was even jailed for contempt of court for 20 days because she refused to name anyone. But in grand jury testimony in January 2005, Trimble identified defendant Ronald Reed as the man who told her to make the call.
Reed is charged with one count of first degree murder and another count of conspiracy to commit murder in the first degree. The prosecution says Trimble's testimony provides evidence for the conspiracy charge, which carries the same sentence as first degree murder -- life in prison.
But Trimble didn't turn out to be the star witness the prosecution expected.
When she took the stand, she said she didn't remember key statements from her grand jury testimony, and that she was heavily sedated from pain medication the day she testified.
During questioning by prosecutor Jeffrey Paulsen, Trimble said she agreed to make the call, but she couldn't recall precisely what she and Reed discussed.
She said Reed told her if she made the call, it would signal to police the whereabouts of a troublemaker in the neighborhood. Trimble said she wanted to get even with the guy because he had robbed her mother.
Trimble said she never expected someone would be killed because of her phone call. What's more, she said she believes that both she and Reed were set up -- that they were "innocent agents," as she put it, in the killing.
She also defended Reed as incapable of killing anybody or of conspiring to get somebody killed.
It wasn't clear for whom Trimble and Reed might have been innocent agents.
Both she and Reed took part in a Black Panther-style organization that helped the black community in St. Paul, but also espoused racial militancy, including protection from the white establishment, and the police.
Trimble struck another blow to the prosecution's case when she further contradicted her grand jury testimony from January 2005.
At that time, she said Reed was with her when she made the fake call from a phone booth. And she described a series of events that would have given Reed enough time to shoot Sackett.
On the stand Wednesday, she told a different version of events that casts doubt on the possibility that Reed had time to shoot Sackett.
But, Ramsey county prosecutors don't have to prove that Reed shot and killed Sackett, because Reed is also charged with conspiracy to commit murder.
Even though Trimble's testimony hurt her credibility, she has consistently maintained Reed convinced her to make the fake call that led to Sackett's death.
The prosecution is expected to continue presenting its case against Reed Thursday. Once the trial is finished, Reed's co-defendant, Larry Clark, will be tried on the same charges, first degree murder, and conspiracy to commit murder in the first degree.