‘Cannon’ test boosts Karen Read’s defense, showing taillight damage consistent with thrown bar glass

Karen Read’s legal team is nearing the end of the case for her defense with crash reconstruction expert Dr. Daniel Wolfe called to the stand Friday.

It was the 28th day of her retrial on murder and other charges in the death of her former boyfriend, a 46-year-old Boston police officer named John O’Keefe. 

Wolfe is the director of accident reconstruction at a firm called ARCCA. 

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Dr. Daniel Wolfe, an expert from the ARCCA crash reconstruction firm, testifies during Karen Read’s murder trial on Friday, June 6, 2025. (Pool)

On the witness stand Friday, he said ARCCA designed a specialized “cannon” to simulate throwing a cocktail glass at Read’s taillight and determined that similar damage could have been caused if someone threw the glass at around 31 mph and 37 mph.

“From the 37 mile per hour test, we are getting damage that’s generally consistent, and by that I mentioned we have portions of the outer lens missing, the underlying diffuser,” he said.

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A photo of Karen Read’s SUV, parked in the Canton Police Department’s sally port, is projected during her murder retrial showing pieces missing from the right, rear taillight, in Norfolk Superior Court, Monday, May 12, 2025, in Dedham, Mass.  (Pat Greenhouse/The Boston Globe via AP, Pool)

“There was also some fracturing on the backside of the assembly. So again we observed damage that was generally consistent with that of the subject taillight.”

Wolfe said he gave an opinion that the damage Read’s SUV was generally consistent with someone throwing that drinking glass at at least 37 mph.

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An image shown in court shows ARCCA’s “cannon” test in which experts fired a bar glass at 37 mph into a Lexus taillight to see how the damage would happen.

In another ARCCA test, the reconstructionists wanted to see if an impact between the taillight and the back of O’Keefe’s head could’ve caused his skull fracture.

Wolfe said he tested at 15 mph. Damage to the test taillight was significantly more than Read’s taillight at that speed – but it didn’t generate enough force to cause a skull fracture.

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Retired Lt. Paul Gallagher, of the Canton Police Department, shows a broken cocktail glass recovered near John O’Keefe’s remains during the Karen Read trial, Monday, May 5, 2025, in Dedham, Mass.  (Pat Greenhouse/The Boston Globe via AP, Pool)

Prosecutors accused Read, 45, of hitting O’Keefe with her 2021 Lexus SUV and driving away as he died on the ground with a skull fracture during a blizzard.

The defense denies that she struck him and has called witnesses who have attributed his injuries to other causes, including a dog bite and a potential fistfight with a man Read was flirting with behind his back.

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Karen Read and John O’Keefe together in an undated photo. (Courtesy of Karen Read)

Special prosecutor Hank Brennan unsuccessfully tried to have Wolfe and a colleague, Dr. Andrew Renstchler, blocked from testifying before the start of the trial.

Wolfe testified during the first trial, which ended with a deadlocked jury, that damage to Read’s SUV is inconsistent with a collision involving O’Keefe.

Karen Read attends her murder trial in Norfolk Superior Court in Dedham, Mass., Tuesday, June 3, 2025. (Libby O’Neill/The Boston Herald via AP, Pool)

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Read told reporters outside court Wednesday that her defense could rest as soon as next Tuesday. There was no court on Thursday.

She could face up to life in prison if convicted. Her first trial, in which the defense claimed she had been framed, ended with a deadlocked jury last year.