MADISON, Wis. -- A man accused of killing a University of Wisconsin-Madison student in 1980 had his conviction vacated by a Dane County judge on Friday.

Ralph Armstrong was convicted of raping and killing Charise Kamps, 19. A judge threw out the murder charges against Armstrong, who was serving a life sentence since 1981 but has always maintained his innocence.

Twenty-nine years ago, Armstrong vowed to to fight his conviction until he could be vindicated.

"I did not kill Charise Kamps," he said at his sentencing. "But I was not able to prove my innocence."

On Friday he came one step closer to freedom.

Armstrong's conviction was overturned in 2005 by the Wisconsin Supreme Court after DNA testing failed to link the now 56-year-old Armstrong to the crime. The Supreme Court ordered a new trial. Armstrong's attorneys argued the charges should be dropped.

Dane County Circuit Judge Robert Kinney ruled Friday that harm done to Armstrong by misconduct by prosecutors can't be fixed and the charges should be dropped.

"Because the defendant's due process right to a fair trial has been irreparably compromised, the defense motion is granted and the case is dismissed," Kinney said.

Kinney found that prosecutors' actions violated Armstrong's rights. Former Assistant District Attorney John Norsetter testified in April that he didn't inform defense attorneys of a reported confession to the crime by Armstrong's brother in 1995. Armstrong's brother is now dead.

Then, after the Wisconsin Supreme Court overturned the case in 2005, Norsetter had evidence tested by the state crime lab without informing defense attorneys, which destroyed it for future testing. Kinney ruled that violated a court order.

"The facts of this case are as unusual as a 500-year flood, but the prejudice to the defense was not an act of nature," Kinney said. "It stemmed from a series of conscious decisions that had very adverse consequences."

Jerome Buting, Armstrong's attorney, said the judge's decision was significant.

"I think the judge really explained that this is a landmark decision, where the prosecution would go to such lengths to hide evidence of innocence," said Buting. "As a result, Mr. Armstrong has been in custody for 29 years."

Buting said now faith should be shaken in the state's crime lab for its part in the evidence issues.

"The way they apparently run the lab in this case, and you have to wonder how many more just like this, these crime lab people have not been used as independent objective scientists; they're partisans," said Buting. "And what faith can you give results that come out of a lab like that?"

For now, Armstrong said he is continuing with his former vow.

"I will fight this until I find an objective group of people who believe me," said Armstrong.

The Attorney General's Office is defending the state crime lab.

"Statements calling into question the credibility or bias of the state crime lab are unfortunate and confusing. It is the duty of the state crime lab analysts to scientifically analyze evidence and objectively report their findings. Law, courts, defense counsel and prosecutors determine how these findings will be used in any particular case," spokesman William Cosh said in a statement.

The district attorney's office had no comment Friday. The district attorney has 20 days to decide whether to appeal, and Armstrong will remain in prison during that time.

He'll also have to deal with a probation hold put on him for a prior rape conviction in New Mexico from when this crime was committed. His defense attorneys said they think that issue could be moot if this dismissal ultimately stands.