Commonwealth v. Read — Trial Archive
Person Nicholas Roberts Trial 1Nicholas Roberts is a forensic toxicologist from the Massachusetts Toxicology Lab who testified for the prosecution in Trial 1, performing retrograde extrapolation to estimate Karen Read’s BAC at the time of the incident. ← All People
🔬 Expert Witness · MA Toxicology Lab

Nicholas Roberts

Trial 1
143 lines 4 proceedings
Courtroom still of Nicholas Roberts.

About

Nicholas Roberts, a forensic toxicologist with the Massachusetts Toxicology Lab, testified exclusively in Trial 1 on Day 18. His role was to convert Karen Read's hospital serum alcohol level—drawn at 9:08 a.m. on January 29, 2022—into a whole blood BAC and then extrapolate backward to estimate her BAC at 12:45 a.m., the time prosecutors identified as her last drink. His calculations placed Read's BAC at that earlier time somewhere between 0.135 and 0.292 g percent, a range the prosecution offered as evidence that Read was significantly impaired when she dropped off John O'Keefe.

Key Points

  • Roberts testified that Karen Read's hospital serum ethanol level of 93 mg/dL, after conversion to whole blood, yielded a BAC of approximately 0.081 g percent at the time of the 9:08 a.m. blood draw — a figure near the legal limit hours after the incident.
  • Using retrograde extrapolation and assuming 12:45 a.m. as Read's last drink, Roberts calculated that her BAC at that time was between 0.135 and 0.292 g percent — a range the prosecution used to argue she was heavily intoxicated when she dropped O'Keefe off.
  • On cross-examination, Roberts acknowledged that the range represented 'almost a sort of 120% swing,' a concession that became a focal point of the defense's challenge to the reliability of the entire analysis.
  • Little established that Roberts's retrograde calculation depended on the assumed timing of Read's last drink and that additional alcohol after 12:45 a.m. could change the calculation. On recross, Roberts confirmed that Read had not supplied the 12:45 time; Little then proposed that it came from a police report but ended the examination without receiving an answer to that proposition.
  • On redirect, the prosecution rehabilitated Roberts by eliciting that a minor shift in the assumed last-drink time — from 12:45 a.m. to 1:00 a.m. — would not significantly change his extrapolation results, limiting the damage from the recross concession.

Trial Record (4)

Trial 1 First Criminal Trial Apr 29, 2024 – Jul 1, 2024 4 proceedings

Day 18

Direct Nicholas Roberts Adam Lally 4 highlights 84 lines spoken
Summary

Toxicologist Nicholas Roberts testified about converting Karen Read's hospital serum result and calculated a retrograde blood-alcohol range of 0.125 to 0.292 gram percent.

Highlights (4)
Quote

“So our values that were calculated for the low was a 0.078 gram percent. The high was a 0.083 gram percent with the average being a 0.081.”

States the serum-conversion results Roberts calculated from the hospital result.

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Quote

“And it's just so that it can encompass essentially anybody within the general population that they would be somewhere in between that lower limit and that upper limit.”

Explains why Roberts presented a broad retrograde-extrapolation range rather than one value.

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Key Moment

Roberts described his forensic-science education, State Police Crime Lab toxicology work, proficiency testing, and the laboratory's accreditation requirements.

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Key Moment

Roberts identified his serum-conversion report and testified that the reviewed medical record reported a serum alcohol level of 93 milligrams per deciliter from a specimen collected at 9:08 a.m.

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Cross Nicholas Roberts Elizabeth Little 2 highlights 49 lines spoken
Summary

Roberts acknowledged that his retrograde blood-alcohol calculation depended on timing assumptions, a hospital test, and variable conversion factors.

Highlights (2)
Quote

“Yeah. You do have to base it on good -- your starting blocks have to be good. So you have to know the times in which the blood was drawn, the time of the incident and essentially what your value was for your BAC.”

Roberts identified the inputs he said were necessary for a reliable extrapolation.

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Quote

“Yeah. There's a large range, like I said, due to the factors involved in the calculation. That's how it gets so large.”

Roberts attributed the breadth of his estimate to the factors in the calculation.

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Redirect Nicholas Roberts Adam Lally 1 highlights 7 lines spoken
Summary

Roberts said a 5:00 a.m. assumed last drink would significantly affect his calculation, while a 1:00 a.m. drink would not.

Highlights (1)
Quote

“It would have definitely caused a different time frame, depending on how long after the incident or the reported last drink, if there was another drink in between there.”

Roberts explained that the timing of any later drink could alter the retrograde-extrapolation time frame.

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Locations Touched By This Testimony

Good Samaritan Medical Center 1 proc