The public defenders for convicted murderer Byron James Shepard began presenting arguments in the death penalty sentencing phase Wednesday as they ask the jury to spare Shepard's life.

Shepard was convicted Monday in the 2017 shooting death of Tecumseh Police Officer Justin Terney. As part of the sentencing phase, the jury will decide if Shepard should receive the death penalty or a prison sentence as punishment for his crime.

Officer Terney, 22, died March 27, 2017 from gunshot wounds he suffered following a shootout with Shepard, who was a passenger in a vehicle stopped by Terney.

Prosecutors, in presenting witnesses for this phase, have pointed out Shepard's criminal history and prior convictions as well as past violence and drug use, arguing that Shepard is a continuing threat to society.

The defense on Wednesday called two expert witnesses to try to explain, not excuse Shepard's behavior, as the defense claims past abuse, trauma and longtime drug and alcohol abuse are mitigating factors.

Dr. Antoniette McGarrahan, a forensic neuropsychologist, testified about spending eight hours with Shepard at the Pottawatomie County Public Safety Center in April 2018 to conduct a series of tests and evaluations.

She talked with Shepard about his childhood, alcohol and drug use that began at an early age, his troubles holding a job as an adult because of his drug use, medical issues and his family life. Based on a series of tests that day, her conclusion, according to testimony, was that Shepard has impulsivity issues and an unspecified neuro-cognitive disorder, as well as planning and problem-solving issues.

Michael Gomez, a child trauma specialist, testified that Shepard experienced childhood abuse and trauma.

But prosecutors, through cross examinations of both expert witnesses, questioned their credibility and even their objectivity since both were hired by the defense and because of conflicting information in their reports.

More witnesses are expected to testify for the defense on Thursday. Once closing arguments are made, the jury will deliberate whether Shepard gets life or death.

Watch for updates.