The theory of the prosecution was that Fry dealt methamphetamine and thought that Cynthia Bell was going to steal from him. As part of the prosecution's case, it put forth an expert who was able to link Fry's gun to the crime scene. They also called five witnesses who testified that Fry confessed to them that he had committed the killings.
On the other hand, Fry's attorneys put on a witness who indicated he witnessed the shootings and said they were not committed by Fry. His defense also included testimony from several witnesses who said that Anthony Hurtz, an alleged drug dealer, confessed to these murders.
Now comes the key. While the third trial was taking place, a private investigator working for Fry's attorneys found another witness who said she overheard Hurtz confess to killing two people. This witness, Pamela Maples, is a cousin of Hurtz.
Since Maples was not on anyone's witness list, the judge wanted to hear what she had to say outside the presence of the jury. After hearing her testimony he decided not to allow her to testify in front of the jury. The judge made this ruling indicating it was his view that as Maples' said she heard Hurtz confess to two killings but not mention that the people killed were Cynthia Bell and her husband, this evidence would be speculative.
After Fry was convicted, his attorneys took his case to the Court of Appeal. That court concluded that Fry had not been denied his constitutional right to a fair trial.
The court found that other witnesses said similar things to what Maples would have said and that the loss of the testimony of Maples was not prejudicial.
The case then went to the next rung up the ladder, the Ninth Circuit Court, which concluded that keeping Maples off the witness stand violated Fry's constitutional rights. But the court indicated it felt compelled to rule against Fry because of a previous United States Supreme Court ruling that a conviction should not be overturned unless the court found that the error committed by a trial court judge "had substantial and injurious effect or influence in determining the jury's verdict."