The chemistry defense can be tried on cross-examination without a defense expert but then it usually fails. A competent defense expert witness improves the odds of acquittal.
The defense was described as follows:
By insisting that forensic chemists conduct accurate and comprehensive analyses, Messrs. Shapiro and Shellow have wrought a revolution in forensic chemistry. The federal government and the states have had to free people on the basis of evidence that just a few years ago would have been sufficient grounds for conviction. Drug enforcement laboratories have had to purchase new equipment. Forensic chemists have had to go back to school to study chemistry. Defense lawyers have had to learn what the “chemical defense” is and how to use it. In short, every courthouse in America, advertently or inadvertently, has been affected by the “chemical defense.”
Judge Wisdom wrote for the United States Court of Appeals:
The day before trial, the prosecution learned that James Shellow, well known as an expert in defending cocaine charges, would join Bockius’s two attorneys who had already filed notices of appearance. Shellow had originated a sophisticated scientific defense grounded in the chemistry of cocaine. In the trial he conducted what may properly be described as an extraordinarily able examination of the witnesses, based on his knowledge of the chemistry of cocaine.
Ten years ago attorney James Shellow concluded that computers small enough to be taken into courtrooms were now powerful enough to challenge the conclusions of prosecution analysts. He now calls a computer expert as a defense witness. The expert testifies that the very data upon which the prosecution relies creates a reasonable doubt. The probability of a not guilty verdict has substantially increased and he no longer limits the use of the chemistry defenses to cases in which no other defense is available.
Technology and Chemical Analysis in Drug Crimes Defense
Counsel faced with defending a substantive drug prosecution is confronted with a two-witness paradigm: the agent and the chemist. It is virtually impossible to shake the testimony of an experienced agent. The methods used by prosecution analysts for drug identifications have evolved. Early methods were easily applied but proved to be invalid. Current methods are more technically sophisticated and may be valid in skilled hands. Even so, they are often improperly applied. However, the unjustified absolute confidence technicians express regarding the correctness of their conclusions remains unchanged.
The current favorite method among forensic analysts is mass spectrometry. The analyst compares the spectrum of the suspected drug with a standard or reference spectrum of the drug. If the spectra are sufficiently similar, the analyst testifies that in his opinion the suspected drug is the same compound as the reference sample.
Modern mass spectrometers contain computers. These computers incorporate spectral libraries containing spectra of hundreds of thousands of compounds. At a keystroke or mouse click, the spectrum of an unknown substance can be compared to each library spectrum. The operator is then presented with an ordered list of compounds whose spectra most closely match that of the unknown. Such lists generally include estimates of degree of match and the probability that the spectrum of the suspected drug is identical to one in the reference library. Crime laboratory analysts rarely use these computerized matches even though the search takes only a few seconds.
Our Milwaukee Federal Narcotics Attorney will investigate your case thoroughly
Technology now permits defense counsel to convert the spectra it receives in discovery to digital form. Using a laptop computer loaded with spectral libraries the defense is now able to compute the match probabilities which the prosecutions technician declined to evaluate. Frequently, these probabilities will create a reasonable doubt.