The ‘CSI Effect’ & Forensic Evidence

People often assume especially juries that when there is forensic evidence available and an expert is testifying in a criminal trial regarding the forensic evidence the truth of what they are saying is absolute and so is the forensic evidence presented.

An effect known as the ‘CSI Effect’ (from the well-known TV show CSI) is causing these problems in criminal trials whereby firstly jurors expect there to be forensic evidence available for a conviction (since most TV Crime shows are based around forensic evidence that is somehow available within minutes or days) and secondly  when that forensic evidence is presented along with the corresponding expert testimony it is all truth and certainty, instead of opinion or just another piece of evidence to be scrutinised.     

However, forensics are often are matter of interpretation and differing opinions. NOT truth but opinion. As forensic science too can play a part in the miscarriage of justice just like eyewitness evidence or any other evidence.  Especially when considering forensic science evidence has 3 stages where errors can occur in either the collection, testing or reporting stages.

For example, the improper or mismanaged collection of forensic evidence can cause contamination issues, where investigators could accidently transfer evidence, or miss-handle the evidence rendering it unsuitable for testing. Errors can also occur in the storing of evidence whereby evidence can either be destroyed or a cross-transfer of evidence can occur.

Additionally, the testing of the evidence may cause issues as to the incorrect procedures implemented on the testing samples, thus, leading to skewed or incorrect results, this can even result in the misidentification of evidence or even false positive results can occur.

Furthermore, forensic evidence is subjected to human error, and the absence of scientific standards, where test such as bite marks, firearms and tool mark impressions are highly subjective pieces of evidence. However, many experts will testify as objective opinion to these types of evidence without any consideration of error rates or the reliability in the testing stage stated in their opinions to the Court.

Even fingerprints which are universally regarded as the most used and infallible way of identifying a suspect is a forensic procedure and is based on a subjective opinion considering the number and placement of loops, whirls and arches present.   

Lastly, errors in the reporting stage can occur where expert’s misread or misinterpreting the results. And because they primarily work for the police/prosecution there is always a danger of them attempting to fit the results to be in line with the investigation. Plus, expert bias and experts testifying outside the facts of their own expertise and not correcting the Court can also be problematic in forensics and skew the forensic evidence results.

In Australia we have had some famous cases that has proven that forensic evidence is fallible and can lead to a miscarriage of justice,

For instance, one of the most prominent miscarriages of justice in Australia is the Lindy Chamberlain case. In this case the Crown relied on forensic evidence created by a NSW forensic lab who claimed that there was foetal blood under the dashboard, the passenger seat hinge, on the floor (under the carpet) and on the zipper of a camera bag.

At the time of the case the NSW Health Commission did not preserve the plates on which the blood tests were conducted or samples of blood for testing by the defence. Later at the inquest into the case the forensic scientist was unable to specifically state the criteria that was used for determining the match or the conclusion criteria used to determine it was in fact human blood. Due to this the convictions were later overturned.

Importantly, the latter report then concluded that the ‘foetal blood’ was actually spray paint used during manufacturing of the car and the error the report concluded was with the lack of expertise by some experts who testified at the original trial of Lindy Chamberlain, and the lack of proper equipment and consultation between experts and the prosecution. Along with, the police placing considerable pressure on the forensic experts to support the Crown case.

Therefore, the CSI effect can have grave repercussions in our criminal justice system. And the public who may one day become the next jurors in a criminal trial must be aware that forensic evidence is just that evidence that they need to consider carefully along with all the other evidence and scrutinize in the same fashion as any other evidence. And then decide whether it is evidence enough to support the guilt of the accused beyond a reasonable doubt.

If you or someone you know has been charged with a criminal offence, contact Rep-Revive Criminal & Employment Lawyers® for a free initial consultation.


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