Former Police Investigator Brett Seacat on Trial for Wife's Murder

June 5, 2013 — -- Attorneys for Brett Seacat, the former police investigator on trial for the murder of his wife in Kansas, said that she was depressed and taking a prescription drug before she killed herself and torched their home.

However, prosecutors allege Seacat, 37, killed his wife, Vashti Seacat, 34, who had served him divorce papers two days prior to her fiery death on April 30, 2011.

They have charged Brett Seacat with first-degree murder, aggravated arson and aggravated child endangerment. The couple's two children, ages 2 and 4, were in the home. Seacat has pled not guilty.

In a Kingman County, Kan., court Tuesday, Brett Seacat's brother, Robert, said that he saw Vashti Seacat the weekend before her death and that she was depressed.

"She looked like she lost a great deal of weight, looked sleepy," he told the court.

A private investigator hired by the defense testified he found several vials of a drug called HCG in the Seacats' home. The defense said Vashti Seacat was taking the drug, which has been known to have side effects leading to depression, in an attempt to lose weight.

Brett Seacat says his wife was suicidal. Watch the "Good Morning America" video here.

However, during an interrogation two weeks after Vashti Seacat's death, investigators told Brett Seacat that his story didn't match the evidence.

"It's our belief you had something to do with this. And ... you had no blood on you, you picked her up in her bed, held her to you close," an investigator said. "If you walked through fire you would have injuries besides a small injury on the top of one of your feet."

During the interrogation, Seacat repeatedly yelled, "No!" at investigators as they asked whether he killed his wife -- outbursts the court heard on recordings presented this week.

Seacat also was heard in the background of a dashboard camera taken at the April 2011 fire telling police his 34-year-old wife was inside the house and that she killed herself.

Seacat told investigators that he reached into his wife's burning bed with his hands, actually picking up her head. But when he realized she was limp and likely dead, he dropped her and escaped.

The jurors saw pictures of Seacat's entire body taken the day after the fire that showed hair on his calves and two blisters on his left foot.

Seacat has claimed he was downstairs sleeping when he heard a gunshot on the night of April 30, 2011, when his wife was killed.

"There's a fire and my wife is ... Oh, I think she shot herself, but she's in the fire," he is heard saying on the 911 call. "Hurry, hurry. I think she's dead. I think she shot herself. Oh, there's smoke everywhere.

Prosecutors have alleged he wrote his wife's suicide note. The prosecution has said Seacat had a clear motive to kill his wife -- the divorce papers she had just served upon him.

One witness said he watched Brett Seacat torching two hard drives around the time of Vashti Seacat's death, and a forensic scientist found traces of gasoline on his pants, according to ABC News affiliate KAKE.

A Kansas Bureau of Investigation agent testified that he found a note in Seacat's pocket the night of the deadly fire with a list that read, "1. Calm--died/accident 2. Her parents 3. Everything that the ... truth." The note also had the phrase "no suicide" on it.

The Seacats' marriage counselor, Connie Suderman, testified that Brett Seacat called her after the fire and said, "I killed her. Vashti is dead and it's my fault."