GREELEY, Colo. -- There's been another strange twist in the fatal love triangle case that has riveted Greeley for more than a year.

On Thursday, Weld County District Court Judge James Hartmann dismissed a tampering with physical evidence charge against Ken Nelson, the estranged husband of convicted murderer Shawna Nelson.

"We didn't feel we could prove the tampering charge beyond a reasonable doubt," said special prosecutor Cliff Riedel. "Ethically we felt we had no other choice but to ask for dismissal."

Authorities filed the tampering charge after a witness told them he saw a man, believed to be Nelson, reach in and take something from the pickup the murder suspect was driving the night Heather Garraus was killed.

Investigators initially thought Ken Nelson may have hid the .40-caliber gun that his wife used to kill Garraus.

But Ken Nelson's own testimony at his wife's trial, and that of Michelle Moore, cast a different light on the evidence.

Nelson told jurors that he and his supervisor, Kell Hulsey, stopped Shawna as she was driving home Jan. 23, 2007, minutes after they had heard on the police radio that Shawna was suspected of killing a woman execution-style in the parking lot of a Greeley credit union.

Shawna had a three year affair with Garraus' husband, Ignacio, and gave birth to his child.

When Garraus found out about the affair, and the baby, she made Ignacio break it off. That didn't sit well with Shawna.

Prosecutors said Shawna was dressed in a grim-reaper mask and black robe when she ordered Garraus to her knees and shot her twice -- once in the back and once in the left temple.

They said Shawna got rid of the robe, the gloves, and the shoes she was wearing, as well as the gun.

They recovered the shoes on a snow bank about 700 feet away from where Shawna was stopped. The mask was still in the pickup.

Ken Nelson told jurors that he did reach into the vehicle and picked up the mask, then put it back down.

Prosecutors also linked two shell casings found at the crime scene to Ken Nelson's duty gun.

During the murder trial, Moore testified that Shawna told her she planned to kill Garraus and that she planned to leave evidence to throw off investigators.

When asked if prosecutors think Shawna planted the casings from her husband's gun at the scene, Riedel said, "That's a very plausible scenario and one that we factored into our decision."

Riedel also said there is other evidence to indicate that Shawna tried to frame her husband. "She was driving his truck, used his gun or shell casings and wore his underwear, socks and cap."

"If he were in fact erroneously convicted of the murder," Riedel said, "Heather Garraus is dead, she's (Shawna) got Ig, she's got the kids and Ken's out of the picture, so the jurors may have considered that scenario, I don't know."

"I'm very thankful that prosecutors decided to dismiss the charges rather than force Ken Nelson through the expense and the anxiety of a trial," said Todd Taylor, Ken Nelson's attorney.

Taylor said Ken Nelson is trying to get on with his life, raising his three children, including the one fathered by Ignacio Garraus.

"They're having some issues," Taylor added. "There's a lot of grief and a lot of pain in this case."

Taylor said Ken Nelson has filed for divorce and that it should be final in about a month.

Shawna Nelson is serving a life term without the possibility of parole for her conviction of first degree murder.

Shawna's family members insist she is innocent.

When asked if Ken Nelson felt the same way, Taylor said, "What he'll tell you is that he wasn't there. He can't say for sure. I think he respects the jury's verdict and has no reason to conclude that the jury made a mistake in Shawna's case."

Read Lance Hernandez' Blogs:

• March 1, 2008: Shawna Nelson Trial Blog: Jury Recesses For Weekend
• February 27, 2008: Nelson Trial Blog Day 5: Forensic Experts Link Casings To Gun
• February 26, 2008: Blog Day 4: Husband, Best Friend Testify
• February 25, 2008: Blog Day 3: Nelson’s Interrogation Tape Shown
• February 22, 2008: Blog Day 2: Suspect’s Lover Testifies
• February 21, 2008: Blog Day 1: 911 Tapes Played