WOODSTOCK – Prosecutors say Tim Smith shot an unarmed man in the back and then tried to cover his tracks by staging a break-in, but the defense painted a picture of a man protecting his wife who didn't mean to kill.

Smith, 28, of Woodstock, is charged with murder in connection with the death of 48-year-old Kurt Milliman of Prairie Grove, a former McHenry County courthouse security officer and Island Lake bar owner.

Police have said that Milliman responded May 28, 2011, to an online ad for sex with Smith's wife, Kimberly, at the couple's home on Doty Road.

In his opening statement on Tuesday, Assistant State's Attorney Michael Combs said Kim Smith "wasn't into it" and told Milliman to leave. Tim Smith had been in the home but in another room, and stepped in.

"This guy lost his cool, he got mad, and he shot him," Combs said. Smith then tried to smash his computer and used his elbow to break a window to make it look as if Milliman was an intruder.

But police confronted Smith with inconsistencies in his story, and he admitted that he was lying, Combs said.

"When you're a lying liar, your story doesn't make sense," Combs said.

Combs also attacked Kim Smith, calling her a "harlot" who was part of the "house of ill repute."

After prosecutors forced her hand by granting her immunity for whatever she says on the stand, Kim Smith is expected to testify. She faces her own charges, including prostitution, but was never charged with murder.

Assistant Public Defender Kim Messer acknowledged that jurors aren't going to like Tim Smith, his wife or Milliman.

But they were all consenting adults, she said.

"This is not a case about intention to kill a person," Messer said. "It is a case about natural instinct to protect."

The Smiths were involved in a "swinger" lifestyle, she said, and that eventually parlayed into having sex for profit.

Because the couple was engaged in an inherently risky situation, Tim Smith had been home in case something happened when Milliman came to the house.

Tim Smith heard his wife tell Milliman to get his hands off her, Messer said. He took his gun and saw Milliman pinning his wife to the wall, so he grabbed Milliman by the collar.

Then Milliman flailed or something happened in the scuffle, and the gun went off, Messer said.

Milliman was shot once, with the bullet entering near his right shoulder blade and traveling across his chest before becoming lodged near his left collarbone.

"Tim didn't want that gun to go off, but it did," Messer said. "He was threatening force to get that man out of the house. The man wasn't leaving."

She acknowledged that Smith did lie to police, but only because he didn't want anyone to know about what he and his wife were doing.

He never denied shooting Milliman, she said.

Other evidence presented showed photographs of the home, including of what appeared to be blood on the floor and wall near the front door. Photos also showed opened and unopened condom wrappers and a $50 bill found behind a toilet.

The first officer on the scene, Deputy Joshua Singer, testified that when he arrived, Tim Smith was on his knees crying outside the home with Kim Smith pacing nearby.

Tim Smith pointed to the gun nearby on the ground and said that he shot a man to protect his wife, Singer said.

The trial was cut short on Tuesday due to snowy weather, but testimony is scheduled to begin again this morning at 9.