The defense team of Derek Chauvin, the ex-cop charged with the murder of George Floyd, brought a medical expert who said during Wednesday's trial that carbon monoxide poisoning might be one of the contributing factors to the Black man's death.

Retired forensic pathologist Dr. David Fowler was called by Derek Chauvin's defense team on the 13th day of his murder trial. His testimony was considered a marked departure from what was previously stated by medical experts called in by the prosecution.

David Fowler, a former chief medical examiner of Maryland, was asked about his opinion on George Floyd's cause and manner of death. This was after he reviewed the death certificate, medical records, and autopsy of the victim. 

Fowler said a sudden cardiac arrhythmia due to his atherosclerotic, and hypertensive heart disease caused Floyd's death during the restraint, Yahoo! News reported. 

He was then asked if he believed there were other factors that could have contributed to Floyd's death. 

Fowler noted that there were several substances, including methamphetamine and fentanyl, that could have been factors. He added that carbon monoxide might also have played a role in the death of George Floyd. 

The medical expert further noted that potential paraganglioma added adrenaline to the whole mixture of the said substances that made things worse for George Floyd.

David Fowler said paraganglioma is a tumor found in the victim's abdominal area during the autopsy.  

READ NEXT: Kim Potter: Cop Who Shot Daunte Wright Resigns, Flees Home

First Mention of Carbon Monoxide in Derek Chauvin's Trial

Fowler's statement was the first time that the potentially lethal gas, carbon monoxide, was brought up during Derek Chauvin's trial and was considered a contributing factor to Floyd's death, CBS News reported.

According to Fowler, when the former police officer subdued George Floyd, the victim was exposed to the vehicle's exhaust, leading to a possible increase of carbon monoxide in his bloodstream. 

Moreover, Dr. Andrew Baker, the medical examiner who performed Floyd's autopsy, noted that the deceased showed recent use of meth and fentanyl intoxication. 

However, state medical examiners have already testified that the amount of substances in George Floyd's body was minimal and could not have played a large role in his death.

With all these contributing factors that played a role during the incident, such as the drug intoxication, natural disease, and the restraint, Fowler noted that he would label George Floyd's cause of death "undetermined," MSNBC News reported.

However, Fowler's professional opinion and conclusion are different from that of the medical examiners who conducted separate autopsies for the victim's family and Bakers. 

Others have all concluded that George Floyd died of homicide. The testimony from Fowler is consistent with the arguments of Derek Chauvin's team throughout the trial. 

It can be recalled that defense attorney Eric Nelson argued during his opening statement on March 29 that Floyd's death was not solely caused by Derek Chauvin's use of force but by other factors as well. 

The defense team is expected to continue their arguments this week. Derek Chauvin is currently facing charges of second-degree manslaughter, second-degree murder, and third-degree murder for Floyd's death. 

George Floyd's death became a high-profile case as it sparked several protests all over the country as people marched against police brutality and systemic racism. 

READ MORE: Medical Expert Defends George Floyd's Cause of Death Focusing on Oxygen Loss

WATCH: Derek Chauvin Trial Continues On George Floyd's Death - Day 13 - From NBC News