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Just how fallible is forensic DNA?
jeeg April 17, 2012 at 3:12 pm #1492
Although DNA detection might have advantages over fingerprint dusting, the test is nevertheless fallible. Environmental factors at the crime scene such as heat, sunlight, or bacteria can corrupt any genetic data. Any DNA evidence must be stored in sterile and temperature controlled conditions. Criminals have been suspected of contaminating samples by swapping saliva.There is room for human error or fraud in comparing samples taken from suspects with those removed from a crime scene. The accuracy of any genetic profile is dependent upon the number of genes examined. Where less than four or five genes can be investigated, the PCR technique serves only to exaggerate any defects or omissions in the sample. In 1995 an 18 month investigation was launched into allegations that the FBI Crime Lab was ‘drylabbing’ or faking results of DNA comparisons.Even a complete DNA profile cannot indicate the length of time a suspect was present at a crime scene or the date in question. The mere creation of a database cannot be the panacea for crime detection.JoseJose April 20, 2012 at 12:48 pm #1536
For all the case-solved moments it provides on television crime dramas, DNA is far from a perfect forensic tool.
Samples can degrade over time, confounding analysis. The handful of gene markers used by crime labs to identify individuals aren’t quite so unique as expected.SanjaySanjay April 20, 2012 at 12:49 pm #1537
Another problem with courtroom DNA is the “CSI effect”: when crime lab analysts know a sample comes from a prime suspect, they’re more likely to make a match.PopGenPopGen April 25, 2012 at 9:15 am #1566
Cryptic Distant Relatives Are Common in Both Isolated and Cosmopolitan Genetic Samples
Although a few hundred single nucleotide polymorphisms (SNPs) suffice to infer close familial relationships, high density genome-wide SNP data make possible the inference of more distant relationships such as 2nd to 9th cousinships. In order to characterize the relationship between genetic similarity and degree of kinship given a timeframe of 100–300 years, we analyzed the sharing of DNA inferred to be identical by descent (IBD) in a subset of individuals from the 23andMe customer database (n = 22,757) and from the Human Genome Diversity Panel (HGDP-CEPH, n = 952). With data from 121 populations, we show that the average amount of DNA shared IBD in most ethnolinguistically-defined populations, for example Native American groups, Finns and Ashkenazi Jews, differs from continentally-defined populations by several orders of magnitude. Via extensive pedigree-based simulations, we determined bounds for predicted degrees of relationship given the amount of genomic IBD sharing in both endogamous and ‘unrelated’ population samples. Using these bounds as a guide, we detected tens of thousands of 2nd to 9th degree cousin pairs within a heterogenous set of 5,000 Europeans. The ubiquity of distant relatives, detected via IBD segments, in both ethnolinguistic populations and in large ‘unrelated’ populations samples has important implications for genetic genealogy, forensics and genotype/phenotype mapping studies.PopGenPopGen April 25, 2012 at 9:17 am #1567
The point of the article above is that in certain populations the likelihood of cryptic or distant relatedness is much higher. Therefore, false positive identifications of crime suspects could be higher.MarkMark June 24, 2012 at 1:09 pm #1714
A clerical error at the Las Vegas police forensics lab led to a man being jailed for a year for sex crimes he did not commit.
Lazaro Sotolusson was scheduled to be tried in two sexual assaults involving juvenile victims. Seemingly conclusive DNA evidence formed the heart of the prosecution’s case, and Sotolusson faced multiple life terms if convicted.
But prosecutors had to dismiss the charges after the police lab acknowldged it had accidentally placed Sotolusson’s name on another man’s DNA sample.NaveenNaveen August 17, 2012 at 2:33 pm #1794
The UK Home Office confirmed its database contains more than 500,000 false or wrongly recorded names. Thats a shocking lapse!RobertRobert October 5, 2012 at 10:51 am #1909
Look at the Shopian murders of Asiya Jan and Neelofar and how poorly handled DNA evidence was. DNA evidence can do far more harm then good when law enforcement doesnt have the capability of handling it properly-mistakes and even intentional mishanding can become common.JohnJohn November 6, 2012 at 1:39 pm #2210
Not to mention the Boston forensic scientist who altered samples to up their conviction rates. Wheres the oversight of labs and personnel??MarshallMarshall December 17, 2012 at 1:20 pm #2912
Two words-human errorShobitaShobita April 1, 2013 at 12:48 pm #3750
Leaving human error aside, the technology itself is exaggerated, bigger databases will necessarily result in more false matches-thats basic math.WilliamWilliam July 8, 2013 at 2:29 pm #4045
I doubt any technology is foolproof, weve only just beguin to learn about genetics, who know what we might learn?VandanaVandana November 15, 2013 at 12:59 pm #4296
Police in many countries are poorly equipped to properly deal with DNA evidence, even in wealthy countries police have made well documented mistakes. The scale of collection of DNA that we are moving towards far exceeds our capacity to properly harness it without prejudice and error.IsaacIsaac May 9, 2014 at 12:45 pm #4461
What about on site Rapid DNA that they’ll be rolling out soon. Police doing all the analyses on site without lab professionals. How could that go wrong??