BROOMFIELD, Colo. — In the final weeks of her life, a man Kristil Krug believed to be her ex-boyfriend sent her threatening and lewd texts and emails that made her think she was being watched. He knew the registration stickers on her license plates were expired and that she had been to the dentist one day, according to investigators.

But shortly before Kristil Krug was found beaten and stabbed in the heart in her suburban Denver home, her marriage was “all but over,” and she thought it was possible that her husband, Daniel Krug, might actually behind the messages, a prosecutor said Friday during opening statements in his trial.

“She was putting the pieces together, and he was running out of time,” Senior Deputy District Attorney Kate Armstrong told jurors about why prosecutors believe Daniel Krug waited for his wife in their garage and attacked her after she returned from dropping off two of their three children at school on Dec. 14, 2023. She said he then used his wife’s phone to send texts, including one in which she claimed to have been having an affair, before driving to his job at the state health department, Armstrong said.

But defense lawyer Joe Morales said there was no physical evidence linking Daniel Krug, 44, to the violent killing, noting that there was no blood found in his car or his clothes, which his daughter said were the same he was wearing when he drove her to the bus stop that morning. None of Daniel Krug’s DNA was found at the scene, though partial DNA from an unknown person was found on her neck, he said.

Morales alleged that sloppy police work had failed to keep Kristil Krug, a biochemical engineer, safe and then bungled the investigation into her death. The detective who investigated the stalking that Kristil Krug had first reported in October 2023 was lazy and incompetent, he said. He also said that police failed to test Kristil Krug’s phone for fingerprints even though they allege that Daniel Krug sent texts from it after killing her.

Morales urged jurors to find Daniel Krug not guilty of first-degree murder, stalking and criminal impersonation and serve as a “barrier” against an unjust conviction.

“You’re the last link in this awful train for this family,” he said.

According to investigators, the email account that was used to send messages to Kristil Krug was created on the computer network at Daniel Krug’s workplace. A burner phone that was used to send some of the texts, purchased with a gift card registered to Daniel Krug, was often found to have been in the same general location as his phone, Armstrong said.

Three of the home’s surveillance camera. which Kristil Krug’s mother said she installed because of the recent stalking, were not recording when she was found, according to Daniel Krug’s arrest affidavit. The one in the garage was covered with tape. Morales said the tape also had DNA from an unknown source.

Prosecutors say Daniel Krug told police that he thought the ex-boyfriend was to blame for her killing. But after police confirmed that man was at home in Utah, an eight-hour drive away, when his wife was killed, he said maybe Kristil Krug was having affairs, Armstrong said.

“It’s always the husband,” Armstrong quoted Daniel Krug as telling detectives as she said he rolled his eyes.

The ex-boyfriend is set to testify during the trial, which is expected to last two more weeks.