Trials of A Forensic Toxicologist: Cross-Examination

At the time I had been at the Centre of Forensic Sciences for about 20 years. The case involved a driver who was intoxicated by alcohol and smashed his car. Fortunately, he was the only one injured and was taken to hospital where a blood sample was collected for medical purposes and seized by the police. I analysed the blood for alcohol by headspace gas chromatography at the lab. The blood alcohol concentration was 0.180 g/100mL. An example of the mixed volatile standard GC output is seen below.

I was at trial to testify on the BAC and the effect it would have on driving ability. The trial commenced, and as usual I was excluded and waited just outside the courtroom until I was called. Typically the forensic toxicologist was the last witness called by the prosecutor in this type of trial. I always joked that I felt like the sanitation worker who cleaned up the mess left by the parade.

While I was waiting, a young local criminal lawyer looked into the courtroom through a window in the door and said to me.“Is that Shelly Altman?”

“Yes”, I replied, looking up from my papers.

“THE Shelly Altman?” he questioned incredulously.

I said, “Yes, he’s from Toronto.”

“He’s a top criminal lawyer. What is he doing here? And who are you?”

I explained to him that Mr. Altman was defending an impaired driving case and that I was the forensic toxicologist who analyzed the blood for alcohol and would soon be on the stand.

“Aren’t you nervous about testifying? He’s a great lawyer and very skilled in cross examination”, the young lawyer said, “in fact I’m going to sit in court right now to watch the cross and learn a few tips” And he did.

Soon afterward I was called to the stand. As usual I initially had to be qualified as an expert in forensic alcohol toxicology. But before the crown attorney (prosecutor) could go through my qualifications, Shelly Altman laconically said, “He’s an expert your honour.” Shelly and I had done a few cases together before and we both respected each other.

After my evidence in chief was concluded by the crown attorney, the judge turned to the defence and said,
“Cross examination, Mr. Altman?”

From the stand I could see the young local lawyer leaning forward in anticipation of a devastating cross. But Shelly got up and said, “No questions your honour”, and sat down.

No questions your honour.

The judge turned to me and said “You are excused Mr. Wigmore.”

I tried not to smile as I walked by the young disappointed lawyer.

This experience illustrates a fundamental principle about cross-examination that many experts learn only after years of testimony: the most effective defence strategy sometimes involves recognising when challenging an expert witness serves no purpose. Skilled defence counsel understand that attacking credible, well-prepared expert testimony can backfire, potentially reinforcing the prosecution’s case rather than undermining it.

In personal injury and overserving liability cases at Wigmore on Alcohol, we’ve observed similar dynamics. When expert testimony is thoroughly documented, scientifically sound, and clearly presented, opposing counsel often recognise that cross-examination may do more harm than good to their case. This outcome reflects not just the expert’s credentials, but their ability to communicate complex forensic toxicology findings in ways that withstand scrutiny.

I can’t remember if Shelly won his case or not, but I think he did. I always try not to be interested in the legal outcome, of either guilty or not guilty. My only concern was the judge’s summary and evaluation of my evidence, that he didn’t find it bias, confusing or unhelpful. Which he didn’t.

Hopefully the young lawyer learned a valuable lesson on how to focus on the legal essentials of the case. I found the longer I was a court-going forensic toxicologist the shorter my cross examinations became.

The relationship between testimony quality and cross-examination length reveals an important pattern. Over 700+ cases of testimony experience, I’ve consistently observed that thorough preparation, accurate analysis, and clear communication reduce the opportunities for effective cross-examination. Defence counsel recognise when an expert witness has left no vulnerabilities to exploit.

This principle applies equally to criminal cases and civil proceedings involving personal injury claims or overserving liability. When blood alcohol concentration calculations follow established methodologies, when documentation anticipates challenges, and when the expert maintains professional objectivity, cross-examination becomes unnecessary or counterproductive for opposing counsel.

The second but more practicable part of what the great legalist John Henry Wigmore said on cross-examination is seldom cited, but it provides good advice:

“You can do anything with a bayonet except sit on it. A lawyer can do anything with cross-examination if he is skilful enough not to impale his own cause upon it.”

At Wigmore on Alcohol, our approach to expert witness testimony reflects decades of understanding cross-examination dynamics. Whether providing forensic toxicology analysis for alcohol-related personal injury cases, THC impairment assessments, or overserving liability matters, we deliver testimony that withstands the most rigorous legal scrutiny.