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OJ SIMPSON CASE: The Importance of Biological & DNA Evidence in Crime Scene Investigations



I mentioned in one of my earlier posts that I would visit these cases from my Forensic DNA & Serology school days. And no, you cannot use any portion of this to pass off as your own school paper! I am breaking this post up into 2 parts. My paper discussed the Scott Peterson and OJ Simpson cases, so I will separate the two cases between two posts to give you a reading break and time to digest. I have extracted portions of my paper to include below for discussion and thoughts. Please note that my paper was written several years ago, so new facts and evidence may have been presented since then, that I will not necessarily address in this post. Some of this may sound elementary and like CSI 101, but keep in mind, I was writing this for my Master's Degree - it will sound like I'm explaining a lot of processes. This should be a good post for a true crime beginner to read!


Also, remember that these are MY opinions, so please be kind. I am not an expert. Most of this was based on three books that can be found on Amazon:

  1. Without a Doubt by Marcia Clark with Teresa Carpenter.

  2. A Murder: From the Chalk Outline to the Execution Chamber by Greg Fallis.

  3. Triumph of Justice by Daniel Petrocelli with Peter Knobler.


I have cited page numbers for reference. This is a controversial topic for some people, so please do not leave rude comments on my page.


The OJ Simpson case was probably one of the cases that made DNA evidence so famous and a common term in every household. This famous and controversial case accused OJ Simpson of the brutal and horrific murders of his estranged wife, Nicole Brown Simpson, and her friend, Ron Goldman. Although OJ had never physically interacted with Ron, prosecutors paint the picture that OJ was jealous and not happy that Ron was visiting Nicole on the evening of the crime. OJ's history of spousal abuse did not help his case either. Prosecutors claim that the night of the murder, OJ went to Nicole's house, witnessed Ron approaching, snapped out of jealousy and rage, and slaughtered them both. I believe DNA evidence and biological evidence played a huge role in this crime, however, the prosecutors did not do a good enough job at convincing the jury as OJ was found not guilty of a crime (in my opinion and after studying forensics and researching this crime) that he did commit. It was a great miscarriage of justice, and it is very embarrassing to read books showing the evidence in plain view and then knowing that the defense was able to plant reasonable doubt in the minds of the jurors. There were also many shoddy mistakes made during the investigation, and much can be learned by forensic students in the mistakes and 'what not to do' during an investigation.


Blood droplets played an important role in this investigation. Since blood droplets were found on many different surfaces, this is almost an ideal topic for a student in forensics. A blood drop found in the driveway behind Nicole's home was good enough to use for RFLP analysis, which is highly sensitive and doesn't work well with degraded DNA (Clark 396). After DNA analysis, it was determined that "only one in 170 million people" would match that DNA, and OJ was the match (Clark 396). Blood found on the gate was in even better shape and was able to be tested more extensively. For this blood, "only one in 57 billion people had that DNA type" (Clark 396). Therefore, this "perfect match" was identified as OJ Simpson. In the bronco, OJ's car, blood was found that belonged to both victims as well as OJ's blood. OJ claims he had never had any physical contact with Ron. If this is true, then why was Ron's blood in OJ's car, mixed with his own blood, if the two had never had any contact (Petrocelli 415)?


The LAPD crime lab used PCR DQ-alpha to test blood samples and evidence submitted in the OJ Simpson case. Al results were consistent. All blood drops collected form the trail at Nicole's home were tested and very single one "displayed OJ Simpson's genetic markers, and only his genetic markers" (Clark 68). From the bloody glove that was collected from OJ's residence, genetic markers were found for both Ron Goldman and Nicole, as well.


Among other evidence found, within the knit cap found at the scene, presumed to be what the killer wore, twelves hairs embedded within the fabric of the cap were consistent with OJ's hair. Blue/black cotton fibers from this cap were also "found on Ron's shirt, Simpson's socks, and the glove" found at OJ's home (Petrocelli 441). This was pivotal in that these fibers linked three separate pieces of evidence in different locations. OJ's bronco contained a carpet of a rare type of fiber, which was found on the glove from OJ's home and the knit cap found at the crime scene. Therefore, this carpet fiber linked both pieces of evidence to OJ's bronco and hence, to OJ.


Presumptive tests were done on several stains at OJ's home that tested positive for the presence of blood. These included "stains in the foyer, on the door handle of the bronco, and on the glove found" (Clark 70). In addition, presumptive tests were also positive for blood on the drains in the master bathroom sink and shower. One problem with this, though, is that since some substances can give false positives with presumptive tests, no other drains in the house were tested. If they had been tested and tested negative, then this would have strengthened the case of the positive test in OJ's master bathroom. But if the other bathroom drains had been tested and tested positive, then OJ either cleaned up from the murder in each of the bathrooms, something in all the drains was giving a false positive, or all the drains in the house contained blood. Only the drains that appeared to be in "recent use" were tested (Clark 70).


According to autopsy reports, Nicole was stabbed five times in the side of her neck, punched in the head, and her throat was slashed from left to right very deeply, almost to her spine, severing both carotid arteries (Petrocelli 429). The direction of the cut was evidence that the killer was right handed. The cut was so deep and clean that the suspect must have been standing behind Nicole holding her head and neck taut with the left hand. OJ also had cuts on his left hand which would make sense since he probably cut himself with the knife as he was slashing her neck. Since Nicole's carotid arteries were ut, this causes arterial spurting and rapid blood loss. Much of the spatter caused from the spurting was probably flooded by the enormous blood loss as Nicole lay on the ground in a fetal position bleeding out (Petrocelli 429).


Ron was also stabbed multiple times and had defensive wounds, which showed there was a struggle. His cause of death was a stab wound that penetrated his aorta causing him to bleed internally. Also, upon the autopsy, blood was found to be pooled into his lower back called the retroperitoneum (Petrocelli 431-2). This is called liver mortis, when blood pools within the lower extremities of the body due to gravity. He also had a stab wound to one of his external jugular veins. As this wound bled, it would not have been as fast as arterial spurting since the pressure of veins is much less than that of arteries. Therefore, the blood slowly would have poured or leaked out until the pressure or blood volume was diminished.


It is important to always follow proper technique when collecting any evidence at the crime scene. Some mistakes were made in the OJ Simpson case when officers used a blanket from within Nicole's home to cover her body as soon as they arrived on the scene. This introduced new evidence into the crime scene and contaminated the original evidence since the blanket from within her house could have contained trace evidence such as semen or hair from OJ since either of these could have been left on the blanket within the house during one of OJ's visits. Another example of a crucial mistake was a vial of blood that was "taken from Simpson at the jail" and subsequently taken to Simpson's home where the criminalist was still collecting evidence (Fallis 69). This vial should have been kept separate from evidence collected from his home and should have been taken, on its own, directly to the lab. This left the possibility that the blood may have been taken to his home to frame OJ for the crime - a theme that was repeated over and over again by the defense team during trial. Evidence samples should always be kept separate from controls and reference standards, and this was a huge mistake that helped plant the idea of reasonable doubt in the jury.


Clothes were examined in his hamper, including a black sweat suit, but not collected into evidence (Clark 376-7). A witness claimed to have seen OJ wearing something similar the night of the crime. The criminalist even had a photo of the hamper with the black sweat suit in it. However he did not process it for evidence because he didn't see any visible blood stains at the time (Clark 377). This was a bad mistake since it is always better to collect more evidence than not enough. In addition, if OJ had been standing behind the victim, he may have received a fine spray of blood and this blood spatter might not be visible on black sweats in normal lighting during the investigation (Clark 377). The sweat suit should have been collected since it was at the top of the hamper and appeared to be freshly thrown in. As to whether or not there was blood evident on the items of clothing, that should have been left up to a laboratory to decide by testing rather than the criminalist to decide by brief observation.


Another problem in the OJ case was that not all blood samples were collected from OJ's bronco. Instead, wrongfully, a "representative sample" was taken from blood smears (Clark 377). However, DNA tests on this "representative sample" showed the presence of Ron Goldman's and OJ Simpson's blood (Clark 377). Had more samples been taken, Nicole's blood might have been present in most areas as well.


Fingernail marks came up in the trial, but I never found anything saying that fingernail clippings of the victim were taken for DNA analysis to see if OJ's DNA was under their nails (Petrocelli 432). The cuts on OJ's hand, the prosecutor felt, could have been caused by scratching or clawing by the victims as they struggled for their lives and tried to fight their attacker.


There were also many problems with the crime scene's LAPD criminalist, Dennis Fung, who was responsible for "gathering ad preserving blood and other physical evidence at the crime scene and transporting it to the lab for analysis" (Petrocelli 416). Many of his actions, in my opinion, are inexcusable as they are common sense in the forensic world.


Fung did not wear protective gloves and collected blood evidence into plastic bags that were left in a broken refrigerator in the evidence truck for over two hours (Petrocelli 417)! Anything stored in plastic should only be kept there temporarily (less than two hours, at the most) so the evidence can be transported to the lab or the evidence processing area to be air-dried and repackaged in paper and then stored properly. Leaving the blood evidence in plastic bags for this long could cause the evidence to deteriorate and can cause the growth of bacteria. The tweezers he used were not sterilized between the collection of each of the blood swatches. This causes a problem because where there was so much blood at a crime scene like this, there are mixes of the victims' and, you hope, the suspect's. Not sterilizing the tweezers could have contaminated victims' blood swatches with suspect's blood when the suspect's blood may never have been present in that sample area (Petrocelli 417).


Contamination was an important issue in this investigation and was the defense's argument. They claimed that evidence had been contaminated and that OJ was being framed. This was something the prosecution had to work to disprove. There were accusations that evidence samples from the crime scene were contaminated with OJ's blood during analysis. This was not possible since the lab analyst working with the blood in the lab took all necessary precautions to prevent contamination. The analyst claims that he worked on OJ's blood on the far side of the lab bench away from the evidence. He also stated that during this time, the evidence samples remained sealed in "envelopes on a table in the middle of the room" (Petrocelli 444). There was no spillage of blood, and it was completely unrealistic that OJ's blood could have shot across the room, penetrated the evidence envelopes and contaminated every single sample of evidence. It was also stated that each blood-soaked swatch sample was "wrapped in a bindle of pharmaceutical paper" and control swatches were also packaged separately (Petrocelli 444). So, it was impossible for OJ's blood to splatter across the room, penetrate each evidence envelope, and selectively decide to only skip the controls.


Precautions that should have been taken to prevent many errors at the crime scene would have been to limit the number of people in the crime scene since there was so much blood and evidence. The more people in the scene, the more the contamination of evidence was likely and the more destruction of evidence was likely such as tracking through blood, and tracking through transfer stains or shoe prints. The investigators also made crucial mistakes such as introducing an item from outside of the crime scene (the blanket from Nicole's home) into the crime scene to cover her body. This may have introduced more evidence to incriminate OJ, even if he was not the killer. Protective equipment should have been used by all personnel on the scene, which should have included booties, possibly medical scrubs, caps, gloves, and hair nets. Better care should have been taken during the collection of evidence and a broken refrigerator should never have been in the evidence van. The refrigerator should have either been replaced or repaired prior to the collection. And if that was not possible, then upholding the chain of custody, an agent or officer should have acted as a courier to transport evidence in coolers directly to the labs every hour where they blood samples could be properly packaged and stored.


One good thing that was done was that the DNA evidence was processed in three separate labs with consistent results every time. This helped the prosecutor's case since the lab could not be blamed for contamination if all samples in all three labs tested the same. It is always better to collect more evidence than not enough. The black sweat suit in the hamper at OJ's house should have been collected for evidence and tested for presence of blood. In fact, any dirty clothes in the hamper should have been collected since he supposedly cleaned up, showered, and changed when he returned home, before leaving for the airport. Towels should have also been collected to see if blood was evident on any of them after drying off from the shower. The laundry room should have also been checked to see if he had attempted to launder anything quickly or if he had thrown any items in the washing machine.


The surplus of biological and DNA evidence in the OJ Simpson case, in my opinion, links him to the murder of Nicole Brown Simpson and her friend, Ron Goldman; however the jury did not convict him of these crimes as reasonable doubt was introduced into the case due to shoddy evidence collection at the crime scene. This proves the importance of chain of custody, preserving and protecting the evidence, and securing and protecting the crime scene. What may seem like a small mistake or oversight can prove to be huge and costly in the court of law. Small mistakes made during evidence collection and processing decreased LAPD's credibility in the eyes of the jury and gave them a reasonable doubt - the jury felt the evidence could have been contaminated with OJ's blood or that he was framed by police.


Here are my current-day thoughts:


I have read several more books on the OJ case since I wrote this. I believe OJ was lucky to not get convicted due to legal technicalities, shoddy police work, and reasonable doubt. But the evidence is still there...


What are your thoughts on this case? Who did it?

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