In your Pennsylvania DUI trial, the district attorney will call an "expert" - typically the forensic chemist from the government crime lab who analyzed your blood or urine sample to determine your blood alcohol content (BAC). The crime lab technician's testimony will always indicate your guilt, but a skilled Pennsylvania DUI attorney from Zachary B. Cooper, Attorney at Law, P.C. knows how to appropriately aggressively cross-examine the district attorney's expert witness and will work to create reasonable doubt as to your alleged guilt.
The district attorney will first ask the crime lab technician to describe the education and training that qualifies him or her as an expert. The district attorney will then ask the technician to testify about your chemical test in your Pennsylvania DUI case.
The district attorney's expert will use general scientific principles and assumptions to make conclusions about your BAC, but these conclusions don't take numerous variables into consideration, such as your metabolism, body size, or stomach contents. Your Pennsylvania DUI attorney will challenge these assumptions and others during cross-examination.
The district attorney may also question his or her expert on the use of field sobriety tests in Pennsylvania DUI investigations and how they are used to measure impairment caused by alcohol or drugs. The expert may provide some input on your field sobriety test performance and what it says about your alleged BAC.
The district attorney's expert may make hypothetical statements in support of the accusation that you were driving under the influence. Experts are permitted to use hearsay - out-of-court statements - to support opinions, conclusions, and hypotheticals.
Once the district attorney has finished questioning the crime lab technician, your Pennsylvania DUI attorney can start an aggressive cross-examination. Your defense lawyer will make an effort during cross-examination of the district attorney's expert to both lessen the impact of the crime lab technician's testimony and weaken the district attorney's case.
Just like the cross-examination of the arresting officer, your Pennsylvania DUI attorney will likely ask the crime lab technician leading questions that require only a yes or no answer. This will allow your Pennsylvania DUI lawyer to make broad statements for the benefit of the jurors and the crime lab expert may appear to be in complete agreement with your attorney's presentation of the case.
Your skilled Pennsylvania DUI attorney from Zachary B. Cooper, Attorney at Law, P.C. will make every effort to minimize the impact of the district attorney's expert's testimony and help create reasonable doubt in your alleged guilt in your PA driving under the influence case.