The few tests that have been made of the validity of forensic fingerprinting have not been supportive of the method.
"Despite the absence of objective standards, scientific validation, and adequate statistical studies, a natural question to ask is how well fingerprint examiners actually perform. Proficiency tests do not validate a procedure per se, but they can provide some insight into error rates. In 1995, the Collaborative Testing Service (CTS) administered a proficiency test that, for the first time, was "designed, assembled, and reviewed" by the International Association for Identification (IAI).The results were disappointing. Four suspect cards with prints of all ten fingers were provided together with seven latents. Of 156 people taking the test, only 68 (44%) correctly classified all seven latents. Overall, the tests contained a total of 48 incorrect identifications. David Grieve, the editor of the Journal of Forensic Identification, describes the reaction of the forensic community to the results of the CTS test as ranging from "shock to disbelief," and added:
'Errors of this magnitude within a discipline singularly admired and respected for its touted absolute certainty as an identification process have produced chilling and mind- numbing realities. Thirty-four participants, an incredible 22% of those involved, substituted presumed but false certainty for truth. By any measure, this represents a profile of practice that is unacceptable and thus demands positive action by the entire community.
Investigations have been conducted into whether experts can objectively focus on feature information in fingerprints without being misled by extraneous information, such as context. Fingerprints that have previously been examined and assessed by latent print experts to make a positive identification of suspects have then been re-presented to those same experts in a new context which makes it likely that there will be no match. Within this new context, most of the fingerprint experts made different judgments, thus contradicting their own previous identification decisions.
Complaints have been made that there have been no published, peer-reviewed studies directly examining the extent to which people can correctly match fingerprints to noe another. Experiments have been carried out using naÃ¯ve undergraduates to match images of fingerprints. The results of these experiments demonstrate that people can identify fingerprints quite well, and that matching accuracy can vary as a function of both source finger type and image similarity.
Complaints have been made that there have been no published, peer-reviewed studies directly examining the extent to which people can correctly match fingerprints to one another. Experiments have been carried out using naÃ¯ve undergraduates to match images of fingerprints. The results of these experiments demonstrate that people can identify fingerprints quite well, and that matching accuracy can vary as a function of both source finger type and image similarity.
Critics of bite mark comparison cite the case of Ray Krone, an Arizona man convicted of murder on bite mark evidence left on a woman's breast. DNA evidence later implicated another man and Krone was released from prison.
Similarly, Roy Brown was convicted of murder due in part to bite-mark evidence, and freed after DNA testing of the saliva left in the bite wounds matched someone else.
Although bite mark analysis has been used in legal proceedings since 1870, it remains controversial. Researchers have shown that the accuracy of a bite mark on skin is limited at best. Skin is not a good medium for dental impressions; it is liable to have a number of irregularities present before the imprint that could cause distortion.
Also, bite marks can be altered through stretching, movement or a changing environment during and after the actual bite.
Furthermore, the level of distortion tends to increase after the bite mark was made. Both studies suggest that for the bite mark to be accurately analyzed, the body must be examined in exactly the same position it was in when the bite occurred which can be a difficult if not an impossible task to accomplish.
Because forensic science results can mean the difference between life and death in many cases, fraud and other types of misconduct in the field are particularly troubling. False testimony, exaggerated statistics and laboratory fraud have led to wrongful convictions in several states.
IP declares that, since forensic evidence is offered by "experts," jurors routinely give it much more weight than other evidence. But when misconduct occurs, the weight is misplaced. IP finds that, in some instances, labs or their personnel have allied themselves with police and prosecutors, rather than prioritizing the search for truth. Other times, IP says, criminalists lacking the requisite knowledge have embellished findings and eluded detection because judges and juries lacked background in the relevant sciences, themselves.
In some cases, critical evidence has been consumed or destroyed, so that re-testing to uncover misconduct has proven impossible. Evidence in these cases can never be tested again, preventing the truth from being revealed.
The identification, collection, testing, storage, handling and reporting of any piece of forensic evidence involves a number of people. Evidence can be deliberately or accidentally mishandled at any stage of this process.