IOWA CITY – A volunteer firefighter’s conviction in the death of his pregnant wife will stand even though there is no direct proof of his guilt, an appeals court ruled Wednesday.

The circumstantial evidence offered by prosecutors against Seth Techel is enough to support the jury’s guilty verdict, a three-judge panel of the Iowa Court of Appeals said. Techel, now 25, is serving life in prison without parole in the May 2012 killing of Lisa Techel in their trailer in Agency, a town in southeastern Iowa. She was four months pregnant with the couple’s first child.

Techel claimed in a hysterical 911 call that he was in the shower early that morning when an intruder broke in, shot his sleeping wife and fled.

Prosecutors said that story was a lie, and that Techel killed his wife because he wanted to be with Rachel McFarland, a co-worker with whom he had spent months pursuing a relationship.

Techel has maintained his innocence and pointed to other possible suspects, including a now-deceased mentally ill neighbor with whom he had been involved in an escalating feud.

The first two trials ended in hung juries, with jurors divided on his guilt. Techel was convicted of first-degree murder and nonconsensual termination of a human pregnancy at the third trial. The case was the subject of a “Dateline NBC” episode.

The appeal focused on a discovery that came just before the third trial: that Lisa Techel had been having an affair with a married co-worker in Washington County, where she was a jailer.