Irish doctor’s testimony seen as crucial in securing conviction of Derek Chauvin

Kilkenny-born Prof Martin Tobin gave evidence in George Floyd trial

Dr Martin Tobin, an Irish pulmonologist who has reviewed the death of George Floyd, told jurors during former police officer Derek Chauvin's trial that "Mr. Floyd died from a low level of oxygen." Video: Reuters

The testimony of an Irish doctor has been described as crucial in ensuring the conviction of Minneapolis police officer Derek Chauvin for the death of George Floyd.

The 46-year-old former police officer was convicted of all three charges against him – second-degree murder, third-degree murder and second-degree manslaughter following the death of Mr Floyd on May 25th last year.

The verdict, which was unanimous, was reached by the 12-member jury after about 10 hours of deliberation.

Kilkenny-born Professor Martin Tobin’s evidence addressed the fundamental question in the case: Did Chauvin’s actions stop Mr Floyd breathing?


Prof Tobin’s actions proved to be devastating for the defence which maintained Mr Floyd died from underlying health conditions or the presence of the painkiller Fentanyl in his system rather than asphyxiation.

The prosecution’s case was that Mr Floyd died from asphyxia, or the deprivation of oxygen caused by Chauvin’s actions in leaning on his back.

In his testimony, Prof Tobin broke down the arrest in vivid detail, even identifying what he believed to be the exact moment that Mr Floyd died.

He analysed the footage of the arrest and calculated that when Mr Chauvin’s toes on his left foot touched the ground during the arrest, 86.9 lbs of weight (39.5 kg) was being applied to Mr Floyd’s neck.

When that foot was lifted, the weight on Mr Floyd’s neck increased to 91.5 lbs (41.2 kg).As a drawing that re-enacted the scene was exhibited in court, Prof Tobin explained that when one of Mr Chauvin’s feet was completely off the ground, “this means that all of his body weight is being directed down, at Mr Floyd’s neck.”

He also said there was no evidence of an overdose. Having examined the footage, Prof Tobin said Mr Floyd was breathing regularly after his arrest.

Prof Tobin, who is affiliated with Loyola University in Chicago, took the witness stand on the ninth day of the high-profile trial.

Under questioning by the prosecution, Prof Tobin said that a healthy person would have died from the same restraint exerted by Chauvin on Mr Floyd. He said Chauvin’s knee remained on the detained man’s neck for three minutes and twenty-seven seconds after he took his last breath. The knee also remained on the neck for two minutes and 44 seconds after the officers themselves found there was no pulse.

He explained that the combination of Chauvin’s use of handcuffs, and the placement of his left knee on Mr Floyd’s neck and right knee on his back, contributed to his death.

The death of Mr Floyd last May sparked a fresh wave of anti-Black racism protests across the United States last summer and gave fresh impetus to the Black Lives Matter movement.

Prof Tobin is from Freshford, Co Kilkenny and has been a doctor for 46 years. He is a world-renowned pulmonologist.

"Not that anybody noticed the accent, but are you from Dublin?" asked prosecutor Jerry Blackwell, which prompted a small moment of levity at what has been a deeply sombre trial.

Prof Tobin told the court that he was trained at University College Dublin. His residency training also included working at hospitals affiliated with Trinity College Dublin.

He earned a British Thoracic Association Research Fellowship at King's College Hospital, London. He has been working in the United States since 1980. He has been Professor of Medicine and Anesthesiology at Loyola University Chicago since 1991 and a pulmonologist at the Edward Hines Jr. Veterans Administration Hospital.

A book he authored on mechanical ventilation has been described as the “Bible” on the topic according to The Lancet, the court heard.

Ronan McGreevy

Ronan McGreevy

Ronan McGreevy is a news reporter with The Irish Times