Good Evidence Deserves Good Analysis

Forensic evidence is a key element in gaining a conviction in most criminal cases. Sometimes the evidence is clear cut as in the presence of fingerprints, DNA or blood evidence of a perpetrator being at the scene or found on a victim. In many cases the evidence is circumstantial trace evidence like hair or fibers or paint fragments. If sufficient circumstantial evidence is present then it is possible to build a definitive case against a specific suspect. However, forensic evidence can become a "Catch 22" and it is important for law enforcement officers to understand the limitations of forensic science.

Advancing Technology - The rapid advancements in science and technology over the last two decades have led to an explosion of new techniques and equipment which are being applied to forensic analysis. Most of these procedures have been developed in university research laboratories and while the science behind their development is sound they have not had extensive field testing and verification in real world forensic laboratories. In addition, the methods for performing these procedures have not been standardized so there is the potential for variable results between different crime laboratories for the same evidence sample.

Fingerprint analysis has been a keystone of forensic analysis for more than a century. Certification programs exist to ensure that fingerprint analysts are perform their analysis accurately and according to standardized procedures. The AFIS and IAFIS systems allow print matching to national database in a standardized procedure that minimizes analyst’s errors. New techniques to enhance and further identify latent prints have been developed. These include the superglue fuming procedure, use of colored powders to enhance the print and Alternative Light Sources (ALS) to help visualize print at the crime scene or on a piece of evidence.

DNA has taken center stage in recent years as the evidence of choice in cases where DNA evidence can be obtained. Unfortunately TV programs like the many CSI variants have led the general public that makes up juries to expect definitive DNA analysis in every case. While the methods for DNA analysis is scientifically proven and sound there is again the potential for variability between laboratories. Standard Accreditation programs like ISO 17025 and Forensic Requirements for Accreditation (FRA) have gone along way to ensure accuracy in this field but variability still exists. Problems in sample collection and storage as well as contamination can complicate DNA analysis and interpretation.

Reevaluating Old Cases -The reinvestigation of old rape and murder cases by analyzing DNA evidence has established the innocence of over 200 individuals who were convicted of the crime before DNA analysis became available. Many of those individuals, like Kennedy Brewer, have served long jail sentences for crimes they did not commit. Brewer had spent twelve years in various Mississippi Jail and prisons, including time on death row, for the rape of a three year old girl that he did not commit. Recently Justin Johnson was arrested for commission of that crime.

Expert Testimony - Brewer and others like him were convicted on circumstantial evidence or in many cases presented by an expert in the field whose credentials have subsequently been called into question. In Kennedy Brewer's case the conviction was largely based on the testimony of a local expert that the bite marks on the victim’s body matched Brewer's dental pattern. Reinvestigation of that evidence by other experts in forensic odentology indicate that the bites marks were from animals and were made on the body after it was dead and disposed of.