Biological evidence consists of any evidence produced from an individual. Blood, saliva, sweat, semen, skin cells/tissue and urine. Due to the DNA characteristics present within this biological evidence scientists can usually match the evidence with an individual if given a sample which has not be contaminated. Hair evidence also falls under biological evidence however can not 100% match with another sample. However hair samples can be cross examined at matches can appear however other testing would be needed in order to identify a suspect. Fingerprints also fall within the category of “biological evidence” and can be a massive part in identifying a suspect using different techniques. Biological evidence plays a big role within any investigation as it is DNA and this cannot be changed therefore factual evidence and is rarely not used within court however can be if something has went wrong within the process of the collection. In order to determine on site (within the crime scene) whether that substance is the substance believed presumptive tests are available. These presumptive tests are efficient as SOCO’s could be collecting a sample of paint thinking it was blood therefore wasting Forensic Scientists time. For example to identify semen within a crime scene a presumptive test using phosphatase paper which will appear blue if semen is present. Once the sample has been identified as biological evidence the evidence should be bagged within the appropriate containers.
Biological evidence should be placed within paper envelopes or plastic bags (If not a swab). The reasoning for this is that if placed within a plastic bag the evidence would decompose and the moisture could possibly destroy the evidence. Swabs of liquid evidence for example blood can be taken and placed into their own air tight container. If there is a dry patch of evidence distilled water can be added to the swab to allow for collection to take place. Fingerprints are dusted for using specific powders depending upon the surface the fingerprint is present upon. Once there is a clear print the fingerprint is lifted using clear JLar tape and then placed onto an evidence card.
If there is a physical piece of evidence with biological evidence located upon it for example a knife with blood on a swab of the blood should be taken and the knife should be placed within a plastic container to prevent any injury during transportation. After every piece of evidence has been bagged the officer needs to tag the container or document the time, date, what the evidence is, where it was found, crime scene number and their full name. This is to allow for a smooth chain of custody.
Biological Evidence within the OJ Simpson case…
Within the OJ Simpson case a lot of biological evidence was present within the murder crime scene of Nicole and Ronald. This biological evidence mainly consisted of blood. This blood matched the DNA markers of Orenthal James Simpson. Other biological evidence consisted of hair fibres and a fingerprint. Within the whole investigation blood evidence was found in numerous areas, the crime scene, Simpson’s vehicle (Bronco) and his property. The blood found within his property and vehicle consisted of numerous DNA markers containing the victims and his own blood. The hair follicles found where located upon the victim Ronald Goldman which within analysing suggested that the specimen belonged to Simpson. However with all this evidence pointing to OJ Simpson as the suspect he was still acquitted from the investigation. There was numerous reasons as to why he was acquitted however one factor was how the evidence was collected by the SOCO’s upon site.
Upon the collection of blood samples, SOCO’s took a number of blood swabs however all were not entered into the chain of custody. These blood samples should have been placed into the chain of custody however were not, placed into the back of a van and left there for around a day. As this investigation was set within Los Angeles the weather is hot and with biological evidence placed within a hot van the evidence would have possibly decomposed causing the evidence to be less reliable within a court of law. Within the collection of the evidence SOCO’s also failed to wear PPE, this suggests that contamination could have possible occurred by transferring their own DNA upon to the evidence. These reasons where argued within court by the defence team suggesting that the forensic collection and police work was “sloppy” and due to the fact evidence could have been contaminated it should not be used within the investigation.
The blood samples where packaged when wet, and not left t dry. This caused critical changes within the evidence as the moisture would have damaged the biological factors. Also the evidence was placed within the same bags as other pieces of evidence causing cross contamination, this led to another argument produced by the defence.
The bloody fingerprint was found by Mark Fuhrman (Lead Detective) upon the gateway of Nicole’s property (The crime scene). Fuhrman noted this within his personal documents however never collected the evidence for DNA testing. If this evidence was collected numerous tests could have been performed upon the fingerprint matching it to a suspect or victim and also an analysis of the blood could have been performed. However as this evidence was not collected or logged into the chain of custody this evidence could not be used within court.
Within the investigation OJ’s blood was found within critical areas of the crime scene, however upon examination EDTA was found within the blood. EDTA is used within blood specimen bottles and is a chemical which prevents the blood from clotting. This chemical is only used within Medical centres and Forensic Laboratories. This chemical is also found within the human blood however only at a small concentration in comparison to the amount used within Laboratories. Prior to this analysation an examiner took a sample of Simpson blood for comparison tests to occur, however this sample was not logged into the chain of custody and no documentation was recorded. This sample of blood went missing for around 3-4 hours, it later reappeared within the laboratories. The examiner could not state the exact amount he took however made a guess of 8mm and when returned there was only 6mm. Due to the high concentration of EDTA this allowed the defence team to argue that this biological evidence was planted in order to frame OJ Simpson.
When analysing the evidence collected by SOCO’s Forensic Scientists used DNA markers in order to define Simpson as the suspect. However this type of testing was very new within the time frame of the investigation, this meant that the scientists became confused with the results as they lacked the knowledge and understanding of the tests. This became apparent when presenting their findings within the court as they did not interpret their findings into language in which the jury would understand. Due to the lack of understanding by the jury, the judge overruled this evidence and it was not used within the case.
Below is an image of Gregory Matheson one of the key Forensic Scientists within the OJ Simpson investigation. Here he is within court presenting his DNA findings in a poor context meaning the jury did not fully understand.
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