The lawyer for one of the Fullerton policemen charged in the beating of a mentally ill homeless man suggested Tuesday that it was medical professionals –- not police officers -– who are to blame for the death of Kelly Thomas.

In the second day of a preliminary hearing to determine whether two police officers should be ordered to stand trial for killing Thomas outside a bus depot in July, defense attorney John Barnett questioned a trauma surgeon about the treatment the beating victim received after he was rushed to St. Jude Medical Center in Fullerton.

Dr. Michael Lekawa acknowledged under questioning from Barnett that paramedics had informed him that doctors at St. Jude hospital had struggled to insert a breathing tube in Thomas following the July 5 incident. Lekawa said that if a breathing tube is not inserted quickly it can lead to a low oxygen level in the blood, and eventually death.

PHOTOS: Kelly Thomas death

But Lekawa, the chief trauma surgeon at UCI -- where Thomas was later transfered -- said records did not show such a problem.

"They did everything right," he testified.

A coroner's report found that Kelly had suffered mechanical compression –- pressure on the body leading to a lack of oxygen and eventual brain death.

Officer Manuel Ramos and Cpl. Jay Cicinelli are charged in Kelly’s death -– Ramos with second-degree murder and Cicinelli with involuntary manslaughter. Both have pleaded not guilty.

The surgeon said he was not initially aware of the officers' actions in the field but once he saw what had occurred he understood how Thomas could have sustained enough compression by the weight of the officers that it caused a lack of oxygen to the brain.

The testimony comes a day after a dramatic video of Thomas’ encounter with police was shown in court.