A 38-year-old man with a long history of mental illness admitted to killing his parents in their Eden Prairie home by stabbing them with screwdrivers and declined Tuesday to accept a plea deal that would potentially reduce his punishment.

Nathan T. Lehman, of Minneapolis, pleaded guilty in Hennepin County District Court to two counts of intentional second-degree murder in connection with the May 25 deaths of Robert Lehman, 57, and Debra Lehman, 58.

The prosecution offered Nathan Lehman the chance to plead to one count of intentional second-degree murder and another of unintentional second-degree murder. The potential sentence would have been roughly 40 years.

However, said defense attorney Bryan Leary, his client chose a "straight plea," meaning his admits to the two initial charges because he wants to take full responsibility for the murders.

That decision means he could be given a longer prison term. His sentencing is scheduled for Jan. 8.

Nathan Lehman also chose to avoid pleading not guilty because he didn't want to put his family and others through a criminal trial.

Two weeks before the killings, Nathan Lehman had been civilly committed as mentally ill. His parents said they were in fear of him because of past aggressive and delusional behavior, court documents said. Police first connected Nathan Lehman to the deaths through several 911 calls over the past 10 years.

Police were called to the quiet cul-de-sac on the 6000 block of Woodhill Trail about 7:20 a.m. to conduct a welfare check because Robert Lehman failed to report for work as an Eden Prairie School District bus driver.

The son told authorities he stabbed his parents with a screwdriver in each hand after arriving at the home in the middle of the night.

Nathan Lehman has been civilly committed as mentally ill and chemically dependent several times since 2014, and he often didn't comply with medication or treatment plans.

Paul Walsh • 612-673-4482