Expert Testimony: Toxicology

The sun rises in the east and sets in the west.  Simple.  But any time any scientific principle much more complicated that that is introduced in court, it must generally be supported by expert testimony.

For example, to contest the results of a breath alcohol reading, one needs an expert who knows the basic principle upon which the breath test is said to be based.

Known as a toxicologist, the expert can also testify about how the human body metabolizes alcohol.

Expert Testimony: What is a Toxicologist?

A toxicologist is an expert who has studied the nature, effects and the detection of poisons in the human body, as well as the treatment of poisoning, including the evaluation of injury due to toxic chemicals, whether in the workplace, medicine, the environment or elsewhere. A toxicologist can assess risks posed by toxins including alcohol.  Alcohol is a poison.  Drink enough of it at one time, and people have in fact died.  Toxicologists point out how the human body processes alcohol from the moment it enters the mouth until the time the body is alcohol free.

Expert Testimony in Criminal Cases

Prosecutors use toxicologists in poisoning cases. Toxicology evidence includes the source of various poisoning agents and the period of time over which they cause injury or death.  For example there was a husband who poisoned his wife over time by giving her a sweetened drink laced with anti-freeze.  The toxicologist helped meet the prosecution’s burden of proving the case beyond a reasonable doubt by explaining how the drink was made, how it tasted and the fatal result on the victim’s body over time.

Expert Testimony in Civil Cases

In civil cases, a toxicologist can examine an individual’s blood alcohol level. Through a process known as reverse interpolation, or inverse interpolation as some courts have called it, a toxicologist can determine whether the person would have exhibited outward signs of intoxication at a given time prior to the test. This is crucial in a case, for example, intending to hold a tavern legally liable for injuries caused by a person who was served alcohol when service of alcohol should have been denied.

In a case I tried, two toxicologists one for each side, drew time lines from the point of the hospital blood test back to the time the individual was served the last drink. Calculations were employed to determine the BAC at that point with variables including body weight, time, health and others.  Based on science they were then allowed to testify to the jury as to what bartenders should have observed and whether the victim should have been shut off.

Toxicologists can also testify as to the unreliability of machines and gizmos that read breath alcohol levels but show a blood alcohol reading. The toxicologist can explain flaws in the device, which despite elaborate calibration and testing procedures, are in reality highly unreliable based on scientific principle. The toxicologist also can explain that the correlation of breath alcohol to blood alcohol varies from person to person, therefore rendering the use of such devices highly questionable based on science.

Expert Testimony: Required Crucial Element

Explaining scientific principles to a court or jury requires expert testimony. For example in a case of a drunk driver causing an accident and serious injury, the toxicologist can estimate blood alcohol levels of the offending driver at relevant times.

For more on expert testimony in personal injury cases click here.

Andrew D. Myers is a personal injury attorney in New Hampshire and Massachusetts.

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