Role of Expert Testimony in Drunk Driving Cases

Role of Expert Testimony in Drunk Driving Cases
When an individual has been charged with drunk driving, the State will often present expert testimony concerning chemical tests. The State is required to provide a proper foundation for chemical tests. However, if the defense can show that the State’s expert lacked the required qualifications or that another key component of a proper foundation for admissibility is missing, the defense can object to the admission of the chemical tests. Although courts may allow an expert to testify regarding the results of tests done by a lab technician under the expert’s direct supervision, the evidence can be excluded if the defense can show that the expert witness had no knowledge about the details of the chemical analysis other than what the technician reported.
The expert witness laws vary by state, as do the need for expert witnesses. For example, a few states have determined that chemical testing is not based on scientific expertise and test results are nonscientific evidence that require no scientific substantiation or expert testimony. Other states have held that evidence of chemical testing is admissible so long as a proper foundation is laid. Most jurisdictions hold that chemical testing evidence is scientific evidence.
In addition, the defense may provide expert witnesses. For example, a forensic toxicologist will review the blood alcohol test and other tests to determine if they were properly administered and returned legitimate results. Where results do not make sense, the forensic toxicologist will challenge the procedures followed or assert that the equipment was faulty or that there was operator error.
Where an individual is charged in a drunk driving accident, an accident reconstruction expert can examine the scene of the accident to determine whether the individual was actually at fault. The expert will likely use police reports, witness statements and other evidence such as damage to the vehicles to assess the mechanics of the accident. The expert’s testimony may affect the jury’s determination of fault in the accident.

Copyright 2012 LexisNexis, a division of Reed Elsevier Inc.