Police rely heavily on the positive identification of evidence in a case and its link to the suspect in solving a crime. In fact, this identification alone often secures a conviction. The police department crime laboratory is, therefore, of singular importance and houses a necessary array of highly trained individuals and technology.
Forensic science is the application of science to the law. It is in the crime laboratory that the forensic scientist plies his or her craft. The field of forensic science is new and hence is constantly growing and changing. Today’s crime laboratory has many specialists. This was not so just a few years ago. In the early days of forensic science, a few scientists had to wear many hats and examine a variety of evidence types. Whereas before one scientist might have tested controlled substances, analyzed blood alcohols and bloodstains, and compared hairs and fibers, now there are specialists, especially in the areas of serology—the study of body fluids—and toxicology—the study of toxic substances (usually drugs) in body fluids. Specialization has come about because of the vast store of knowledge needed to interpret myriad evidence resulting in a final answer.
Lab Requirements
The basic equipment and supplies needed for a crime laboratory vary with the types of analyses performed. Before equipment is purchased, some considerations and a commitment must be made. Qualified forensic scientists are hired, with degrees in chemistry, biology, or one of the related sciences. Support personnel are also hired to type affidavit reports, file, and so forth. An area for the laboratory must be designated that is safe for the storage of hazardous chemicals, well ventilated, and secured by alarms, with entry allowed only to the forensic scientists. A separate area is set aside with its own alarm and lock for the securing of evidence and controlled substances.
The funding agency for the laboratory should underwrite any ongoing training expenses. Approximate cost for this additional training was $3,000 per person per year as of 1995. At no cost to the agency, though, are training seminars given at the FBI Academy in Quantico, Virginia. The FBI seminars cover a multitude of forensic subjects. One training course that does have a fee, but is invaluable, is the Forensic Chemist’s Seminar at the Drug Enforcement Administration Training Center in McLean, Virginia; this excellent course deals with controlled substance identification methodologies. Because forensic science is currently evolving at a fast pace, membership in forensic societies is essential to keep abreast of new developments. Two such societies are the American Academy of Forensic Sciences and the American Society of Crime Laboratory Directors. Besides the national ones, regional forensic societies offer many learning opportunities.
A Drug Enforcement Administration (DEA) license is needed to purchase, handle, use, and store controlled substances, as is a state license. General laboratory supplies cost approximately $20,000 in 1995. In a typical police crime lab a visitor sees lab coats, test tubes, racks, microscope slides, spot plates, scissors, weighing papers, spatulas, tweezers, gloves, chemicals, a safety shower and eyewash station, spill pillows, safety blankets, safety goggles, a refrigerator/freezer, a burn station, a first-aid kit, a flammable storage cabinet, an acid storage cabinet, and fire extinguishers. The controlled substances acquired are for use as primary and secondary standards. The equipment and supplies listed next pertain to specific types of examination:
• Marijuana identification: stereo microscope, reagents, thin-layer chromatography tanks, sprayers, silica gel plates
• Blood alcohol analyses: blood alcohol kits, gas chromatograph, column, compressed gases, recorder, miscellaneous supplies (an automated headspace gas chromatograph is expensive, but the best)
• Controlled substance analysis: Physicians’ Desk Reference, analytical balance, ultraviolet viewer, microscope, fume hoods, infrared spectrometer, compilation of known spectra, pellet maker
• Firearms: comparison microscope with fiber optics, workstation complete with tools and supplies, shooting tank (horizontal), reference collection of firearms for parts, subscriptions to firearms journals/magazines, membership in Association of Firearm and Toolmark Examiners
• Library: forensic texts, catalogs from laboratory supply companies
Evidence Submission Procedure
The police crime lab devises and enforces a procedure so that evidence is always submitted in the same manner and to the same place. Evidence envelopes and seals are provided to the submitter for packaging the evidence. Evidence envelopes contain the following information: suspect’s name, report number, incident, date of incident, submitting officer’s name, date of submission, and completed chain of custody. After the evidence is packaged, it is sealed with an evidence seal, on which are placed the sealer’s initials, service number, and date. The chain of custody is a most important step in the process. Depending on the laws of evidence endorsed by courts in the area, it might be required that every person who has custody of the evidence— no matter for how brief a time—must sign the chain of custody. An alternative might be that every person who opens the evidence must sign the chain. The officer who collects the evidence at the scene of the crime is the first name on the chain, and next to his or her name is the date. On the next line is the name of the second person to receive the envelope, and so forth. Defense attorneys look for a broken chain of custody or a shoddily done envelope to discredit the evidence.
Evidence must also be packaged properly, so that no part of it is damaged or lost. Controlled substances must be tightly sealed to avoid leakage, arson evidence put in cans to avoid evaporation, blood tubes protected from breakage, and wet evidence completely dried before packaging. Evidence of any type is never packaged in plastic because it promotes mold formation; paper is used. An evidence analysis request form should clearly state what analysis the forensic scientist is to perform.Cases are then assigned for evidence analysis on a first-come, first-served basis, unless a certain urgency exists. The evidence stays in the evidence vault until called for by the examiner, who opens the package without damaging the collecting officer’s seal, if at all possible. After analysis, another seal is affixed by the examiner, with his or her initials, service number, and date. The evidence is then returned to the vault, awaiting either pickup by the law enforcement agency or destruction.
In any case where source is to be determined, such as blood or semen, known samples must be submitted. This requirement is critical in homicides and sexual assaults. Known blood and semen must be collected from both victim and suspect for proper identification of origin.
Court Testimony
By the very nature of their work, forensic scientists are expert witnesses in court. They possess knowledge and skill outside of the range of the average person when it comes to identification of evidence. But to be a good expert witness requires skill of a different sort—a skill in communication. Complex chemical and biological reactions must be explained to a jury of ”peers,” who might possess knowledge of varying degrees, from that of a high-school dropout to that of a nuclear scientist. So it is imperative that the forensic scientist in the role of expert witness make eye contact with the jury and communicate his or her laboratory findings plainly, accurately, and unequivocally.
