Medics were led astray by unconscious biases, says doctor in Hamilton paramedic trial

Dr. Pat Croskerry says it seems the two paramedics on trial were led astray by unconscious biases that ultimately led to the death of Hamilton teenager Yosif Al-Hasnawi.

Steven Snively, Christopher Marchant are charged with failing to provide necessaries of life

Yosif Al-Hasnawi recites the Qur'an during a religious ceremony moments before he got into an altercation outside the Al-Mustafa Islamic Centre, and was shot and killed. (Al-Mustafa Islamic Centre)

A doctor specializing in clinical decision making says two former Hamilton paramedics on trial seemed to be led astray by unconscious biases that ultimately led to a teenager's death. 

Dr. Pat Croskerry, director of Dalhousie University's critical thinking program, said Steven Snively, 55, and Christopher Marchant, 32 would have been unaware of the biases in their minds that compounded over the night of Dec. 2, 2017. 

So, when they latched onto information that Yosif Al-Hasnawi had been shot with pellet gun, he said, there was little people could do to change their minds. 

"As these things gather momentum, dissenting views are seen as less and less credible," Croskerry said.

Snively and Marchant face the criminal charge of failing to provide necessaries of life for Al-Hasnawi. The 19-year-old was shot at Main and Sanford in Hamilton at 8:55 p.m. and was pronounced dead at St. Joseph's Hospital about one hour later. 

Both paramedics have testified in their own defence that they thought the teen was having a psychiatric emergency. It took paramedics 23 minutes to leave for the hospital, the court has heard.

They also thought the teen was shot with a BB or pellet gun. But Al-Hasnawi was actually shot with a .22 caliber handgun, and its hollow-point bullet perforated an artery and vein. 

Eight biases

Dr. Pat Croskerry is the defence's latest witness. His research focuses on patient safety, clinical decision making, diagnostic failure, and affective and cognitive de-biasing. 

He wrote a report about eight biases he believes came into play the night Al-Hasnawi died. 

"If something goes wrong in clinical practice, it's usually due to the intrusion of a cognitive bias," Croskerry said. 

Pervasive pellet gun rumour

The initial dispatch to paramedics said Al-Hasnawi was shot with a BB gun and had a superficial wound to the abdominal area.

Marchant testified that a firefighter also said it was a pellet gun injury, and both defendants said they heard an officer use the words "pellet." Previous testimony said people in the crowd were also offering their opinions. 

Croskerry said the paramedics "anchored" to this idea of a pellet gun, which was the most influential bias of all that night.

Anchoring "can get you into trouble," Croskerry said. It's often the bias that first appears, and health care workers need to be willing to adjust when new information comes available, he said. If not, the patient can suffer "significant consequences." 

When a person has one bias, he explained, it gathers steam and feeds into the others. 

Croskerry said the pellet gun belief gathered momentum like a rumour among the emergency responders, leading to a group think bias. 

Even though more evidence isn't being added, he said, discussion "fuels" the dominant view. 

"The more that the group tends to go down that path, the less likely they are to listen to conflicting or challenging information," he said. 

As the biases snowball, people are set up to "see what they expect to see" like a filter, he explained. Repeating the message makes it stronger, and competing views are blocked out. 

"You're finding things that are supporting what you've come to believe," he said of the paramedics on scene. 

The doctor also noted that as Al-Hasnawi became more agitated over the night, the paramedics testified they made efforts to calm him down. 

This too was an error, he said, because it assumed he had control over what he was doing. But as oxygen to the teen's brain depleted and blood pooled in his body, Croskerry said, this wasn't the case. 

Croskerry said the more powerful way to establish the truth is to look for disconfirming evidence — things that don't fit in. But he couldn't say if paramedics had this type of training. 

Jeffrey Manishen, representation for Marchant, asked if biases might have still been affecting the paramedics while staying in the ambulance and selecting a hospital destination. Croskerry replied that they would be. 

The caveat, he told the court, is that while biases provide an explanation for human behaviour, you can't really prove it. 

The trial began at the John Sopinka Courthouse in Hamilton on Nov. 24 and is continuing online. It is a judge-only superior court trial, and will be decided by Justice Harrison Arrell. 

Crown attorneys are Scott Patterson and Linda Shin. 

Jeffrey Manishen of Hamilton represents Marchant and Michael DelGobbo represents Snively. 

The person who shot Al-Hasnawi, Dale King, was acquitted last year of second-degree murder. That case is being appealed.