DES MOINES (AP) — Prosecutors have filed their arguments in the appeal by a man convicted of fatally shooting his parents and three teenage sisters.

Shawn Bentler was convicted of five counts of first-degree murder in May 2007 and is serving five life sentences. Authorities said he drove from his home in Quincy, Ill., in October 2006 and murdered his family in their rural Bonaparte home in southeastern Iowa.

Bentler is appealing his case to the Iowa Supreme Court. He asks the high court to reverse the conviction and sentence and send the case back to district court for a new trial.

Bentler’s lawyer filed his arguments in the case earlier this week. In the brief, Bentler claims a district court judge should not have allowed the clothing he was wearing when he was arrested to be used as evidence at his trial.

A key piece of the prosecution’s evidence was a pair of socks he was wearing when he was arrested. On them was a drop of his mother’s blood placing him at the scene of the murders.

Bentler argues in his appeal that the seizure and initial examination of his clothing violated his constitutional rights. That’s because investigators with the Iowa Division of Criminal Investigation didn’t have a warrant to take the clothes from the custody of the Adams County, Illinois, jail, he claims.

In arguments filed on Friday, prosecutors said Bentler’s clothing was lawfully seized.

“Once his clothes were lawfully in the possession of police, defendant no longer had a reasonable expectation of privacy in his clothes and they lawfully could be released to Iowa agents for examination and testing,” prosecutors said.

Even if the clothing was unlawfully seized, prosecutors said the agents later obtained a search warrant so “the taint of any illegality was purged.”

“Finally, even if the district court erred in denying Bentler’s suppression motion, any error would be harmless in light of the overwhelming evidence of Bentler’s guilt,” prosecutors argued.