SANTA ANA (CNS) - A forensic pathologist who works for Orange County today backed up testimony of the autopsy surgeon that a homeless man involved  in a struggle with Fullerton police two years ago died because his breathing  was restricted during and as a result of the fight.

Dr. Anthony Juguilon was called to testify to rebut two defense  witnesses who said Kelly Thomas died from a methamphetamine-diseased heart and  not as a result of ``chest compressions'' during his battle with police,  including defendants ex-Officer Manuel Ramos and former Cpl. Jay Cicinelli, who  are charged in connection with the transient's death.

Juguilon -- who said he has done about 6,500 autopsies in his career --  testified that the cause of death for Thomas was ``prolonged mechanical chest  compressions and blunt facial injuries.''

In other words, the weight police applied to restrain the 37-year-old  Thomas restricted his breathing, making it harder for him to get oxygen into  his system, which led to brain and organ failure, the pathologist testified.  Also, Thomas' broken nose led to bleeding that also restricted his breathing,  Juguilon said.

Dr. Steven Karch, a heart specialist who has written multiple text  books, including one on the pathology of drug abuse, testified  Wednesday that  Thomas was suffering a ``psychotic episode'' during his July 5, 2011, struggle  with six officers, including Ramos and Cicinelli. Also, his heart gave out  because it was significantly weakened over the years due to methamphetamine  abuse, Karch testified.

Dr. Gary Michael Vilke, an emergency physician at UC San Diego,  testified Monday about studies he helped lead in the effects of chest  compression and restraining suspects. Vilke testified that Thomas was breathing  throughout the conflict because he was hollering for help.

Juguilon said he disagreed with Vilke's assertion that Thomas' facial  injuries did not contribute to his death. Juguilon said the surveillance video  of the conflict at the Fullerton Transportation Center confirmed his suspicious  that Thomas choked to death.

``The video evidence for asphyxia is compelling,'' Juguilon said. ``You  can actually hear Mr. Thomas say he can't breathe... His (voice) progressively  declines and ultimately ceases. This is consistent with respiratory arrest.''

Juguilon added, ``The video clearly shows mechanical compression of the  chest and torso.''

A brain starved of oxygen for three or four minutes will suffer  irreversible damage leading to organ failure, Juguilon said.

Juguilon disagreed with Vilke's testimony that Thomas' cries for help  showed evidence he was breathing properly.

`If he's talking or yelling that means he's breathing, but it doesn't  mean he's breathing effectively or efficiently,'' Juguilon testified.

Juguilon backed up testimony from Dr. Michael Lekawa, who treated Thomas  after the struggle at UC Irvine, that the transient's struggling with police  would also deplete his body of oxygen.

Ramos' attorney, John Barnett, repeatedly questioned Juguilon's  expertise in the area of heart disease, pointing out that Karch and Vilke have  done groundbreaking research in their fields.

Juguilon said he was aware of their research, including Vilke's studies  that debunked a prevailing belief in the early 1990s that the way suspects are  restrained could affect their breathing.

Juguilon acknowledged under Barnett's questioning that there is no  research proving prolonged mechanical asphyxiation, but the pathologist said it  is a commonly accepted theory.

'`Mechanical asphyxiation is a phenomenon accepted by every mainstream  pathologist,'' and it is commonly articulated in text books scientists rely on,  Juguilon said.

Barnett pointed out that Vilke did a study that placed 200-pound weights  on volunteers to research how much it restricted breathing.

``But the caveat is he did it for 60 seconds,'' Juguilon said.

Cicinelli's attorney, Michael Schwartz, asked Juguilon about his medical  group's contract with the county.

``It's up again Jan. 14 in a few weeks isn't it?'' Schwartz asked.

Juguilon acknowledged that the contract will be considered next month.  His group won the contract in 2010 with the lowest bid, he said.

Jurors were instructed to return to court Jan. 6 for the last of the  rebuttal testimony from prosecutors. On Dec. 27, attorneys will return to court  in what may be a closed hearing.

On Wednesday, prosecutors filed a motion demanding the personnel records  of Ramos and Cicinelli, who stopped working for the city a year after the  struggle with Thomas.

Michael Gennaco led an independent investigation for the city of the in- custody struggle with Thomas. City officials would not say if Ramos or  Cicinelli were fired.

Prosecutors want the personnel records of Ramos and Cicinelli to rebut  Fullerton Cpl. Stephen Rubio, who testified this week that the two officers  mostly acted within the city's policy when they dealt with the suspect.

``This evidence would be relevant and material to the trial in this  action in light of the defense testimony of Fullerton Police Department  Corporal Stephen Rubio in which he testified there had been no violation of  departmental policy by defendant Cicinelli and only a `slight' violation of  departmental policy, if at all, by defendant Ramos,'' prosecutors wrote in the  motion pending before Orange County Superior Court William Froeberg.

Ramos is charged with second-degree murder and involuntary manslaughter  and Cicinelli is charged with involuntary manslaughter and excessive force.

Police were summoned to the transportation center in response to a call  from a nearby nightclub that someone -- investigators later determined Thomas  was not involved -- was trying to break into cars in the business' parking lot.

What began as a routine meeting between Ramos and two other officers  escalated into violence as Thomas refused to tell them his name and carried on  a prickly and sarcastic back-and-forth with his questioners, according to  surveillance video of the conflict that was shown to jurors.

Thomas died at UC Irvine Medical Center five days later after being  taken off life support.