A 56-year-old man was convicted Tuesday of two counts of abusing a corpse after investigators said he covered his dead roommate’s body with a mattress and other household items and then had sex with a different woman “multiple times” on top of the corpse.

A Multnomah County jury unanimously convicted Clayton Lamont Howard on two counts after a 10-day trial in which Howard served as his own attorney. He is scheduled to be sentenced Dec. 3.

Howard was in prison for 35 years and released in 2017. He was convicted of multiple rape and robbery charges in 1982, according to state records.

Officials said that Neta Mangum, a 59-year-old woman living with Howard at the time of her death, died of a drug overdose March 21.

According to court records, Mangum’s family couldn’t get in touch with her and believed someone else was using her phone to respond to their text messages. Mangum’s family told the court they “knew immediately,” based on the texter’s style and substance, that Mangum wasn’t the texter.

Mangum’s family reported her missing the night of March 22. When police arrived they discovered Howard and the other woman.

Police said Howard had Mangum’s phones, credit cards and some jewelry at the time of his arrest. The jury acquitted Howard on one identity theft charge.

Clayton Howard was convicted of abusing a corpse.

The woman with Mangum told investigators she met him and Howard “several days” earlier and said Mangum told her she could move in to “get off the streets.”

The new roommate told police she last saw Mangum “in the very early morning hours” of March 21.

When the woman woke up in the living room several hours later, Mangum was nowhere to be found, court records said.

Howard told the woman Mangum went to the coast with a guy named Elvis and said she would return March 24.

According to prosecutors, Howard had covered Mangum’s body with clothes, plastic containers and a mattress. He and the woman continued to use drugs, prosecutors say, and then had sex “multiple times” on the mattress that Howard placed on top of Mangum’s body.

The woman told investigators she did not know where Mangum was.

During the trial, Howard told the jury he didn’t call 911 after discovering Mangum had died because he had previously been ordered by his parole officer not to be around Mangum and he feared being arrested.

He also said he had tried to perform first aid and covered her corpse in response to her “dying declaration.”

The jury didn’t agree.

Howard was also found in contempt of court during the trial for cursing at a witness after her testimony.

Staff reporter Noelle Crombie contributed to this report

-- Andrew Theen

atheen@oregonian.com

503-294-4026

@andrewtheen

Visit subscription.oregonlive.com/newsletters to get Oregonian/OregonLive journalism delivered to your email inbox.