A Colorado man accused of killing his wife claimed she had been suffering from postpartum depression and cut her own throat — an explanation police quickly disputed before they arrested him, authorities said Wednesday.

Patrick Barnett, 40, of Lakewood, was charged with first-degree murder, tampering with a deceased body and tampering with physical evidence, the First Judicial District Attorney’s Office announced.

Lindsey Barnett, 37, was found with her throat slit in the shower stall of the couple’s Lakewood home on Aug. 13, according to an arrest affidavit prepared by Detective Victoria Wagner.

Patrick Barnett called 911 at 6:01 a.m. that day and “indicated that his wife” had “cut herself and her throat,” the affidavit said.

But investigators immediately doubted his account. Crime scene investigators found “a large amount of blood on the right side of the bedsheets, pillow,” and “blood clots all over predominantly the right side of the bed,” according to the affidavit.

“A trail of blood was running from the right side of the bed to the bathroom,” but investigators “indicated to me that there was not a lot of blood in the bathroom to speak of,” Wagner wrote.

Police also found that Patrick Barnett had a “new or fresh cut to his right thumb,” along with “fresh scratches on his right upper arm near his arm pit that follow down to part of his chest,” the affidavit said.

He also had “scratches to the bottom right side of his abdomen and a new or fresh scratch mark just below his collar bone,” the document said.

“These scratches mentioned above are consistent with fingernail scratches that are consistent with being defensive wounds,” police concluded.

In his initial interview with police, Barnett admitted that he and the victim had been struggling in their marriage. Lindsey Barnett had suffered from postpartum depression, her husband is alleged to have told police.

The victim’s mother, Donna Ott, told police that her daughter, a teacher, had suffered with depression but “never expressed suicidal thoughts and never had suicide attempts,” according to the affidavit. Ott said, “Lindsey loved her children and was making plans for the school year.”

The couple had two children — age 3 and an infant — who were not injured, police said.

Patrick Barnett insisted to investigators that he and his wife were working to repair their marriage. “He was asked about infidelity by either him or Lindsey and he said there was no infidelity,” the affidavit said.

Hours after Lindsey Barnett’s body was found, police got a call from a woman claiming to be Patrick’s girlfriend asking for a welfare check, police said. She told police she hadn’t heard from him since 11 the previous night, which she said was unusual since the two texted constantly, according to the affidavit.

When police arrested Patrick Barnett at 7:10 p.m. that day and confronted him about the girlfriend, he confirmed he had been seeing another woman, authorities allege. The two had met online three months earlier and bonded over their shared involvement in the Ultimate disc community, police said.

“He admitted he had a relationship” outside of marriage but claimed “Lindsey knew about it and was fine with it,” the affidavit said.

Patrick Barnett was assigned a public defender, prosecutors said; a representative for that office could not immediately be reached for comment Thursday. Barnett is scheduled to appear before a Jefferson County judge Friday.

Lindsey Barnett taught art at Hutchinson and Westgate elementary schools, campuses of Jeffco Public Schools in suburban Denver.

“Lindsey was a joy to have in our school. She brought a deep passion for teaching art, a sweet soul, and an extraordinary dedication to our students,” Hutchinson Principal DeAnn Hoffman said in a statement.

“Beyond her work in the classroom, she always put our kids first, helping organize special projects and pouring her heart into the district art show for both of our school communities. This loss has shaken our entire community, and our deepest sympathies, thoughts, and care are with Lindsey’s family during this difficult time.”