SCOTT PETERSON 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 one book that can be found here on Amazon: A Deadly Game by Catherine Crier. I have cited page numbers in the book at the end of the post for reference. By the way, I HIGHLY recommend this book!

In the Scott Peterson case, Scott was the prime suspect in the disappearance and murder of his wife, Laci, and unborn child, Conner. Although many items of evidence were collected, including both biological and DNA, personally, I don't think this evidence tied Scott to the crime, yet he ws convicted of both murders. There were many items collected and processed as I will discuss, but there were also items that I feel could have been processed and collected that I never found any documentation of in my research. The lack of blood evidence here played a role in determining the most likely scenario of the events leading up to Laci's murder.

Laci Peterson was reported missing by her husband, Scott, early in the evening on Christmas Eve, 2002. He claims he last saw Laci when he left to go fishing around 9:30am that morning (Crier 5). However, no one (friends or family) had spoken to Laci since the evening before. It will never remain clear as to when her death occurred - late December 23 or Christmas Eve morning. In April 2003, her torso washed up along the banks of the San Francisco Bay, just a day after her unborn son, Conner's, fetus washed up across the bay (Crier 343). Scott was arrested and ultimately convicted by a jury of his peers to murder in the first degree for Laci and murder in the second degree for Conner, and sentenced to the death penalty. He has never confessed to the murder and continues to claim he is innocent.

Items of biological evidence were removed from Scott's home a few days after Laci was reported missing. Officers were looking for any evidence that might suggest a struggle. Therefore, they checked baseboards, crevices, and the bottoms of furniture as these could all be places that might contain blood spatter; and if the crime scene had been cleaned up by the suspect, they may not have reached or thought about these areas.

Scott's truck was examined and stains and items of interest were collected. Four small bloodstains were found on the interior side of the driver's door, and a suspected bloodstain was found on the back of the steering wheel. A presumptive test, Hemo-Glow, was used to test these stains for the presence of blood. All stains that were sprayed with Hemo-Glow thin the truck were positive for blood (Crier 84). Ultimately, these blood spots were all tested to be from Scott, not Laci. Some of Scott's clothes were also collected as evidence even though the clothes may have been washed. Jeans and other items that were believed to have been worn by him on the day of Laci's disappearance were taken. Investigators were more than likely hoping to find blood spatter, or other biological evidence that linked Scott to Laci and her death. It is important to collect items of clothing even if blood is not visible since high velocity spatter can actually embed itself within the fibers of the clothes making it almost impossible to see on first glance and in normal lighting. Scott was also a hunter and fisherman, so any blood detected on his clothes or in his car needed to be tested for human blood since he could have fish blood or other animal blood on this clothes and in his car. Leucomalachite Green (LMG) was used as a presumptive test on many stains and was shown to test negative for blood on Scott's shoes and in some portions of his boat (Crier 456). LMG tested positive for the presence of blood in other sections of the boat and on the couple's bed sheets (this blood was determined to be from Scott through subsequent testing) (Crier 452).

Four hair brushes and two toothbrush heads were also collected (Crier 95). The hairbrushes could be used to compare Laci's hair to any other hair found as evidence. The toothbrushes could provide DNA samples for Laci and Scott, in the event that Scott refused to cooperate with police. A single dark hair was found on a pair of pliers in Scott's boat. it was consistent with a hair from Laci's brush. Mitochondrial DNA testing had to be used since the hair from the pliers contained no root (Crier 327). When the hairs were compared for a match, the evidence "appeared to be in the same range of variation" (Crier 327).

Two vacuum cleaners were also taken. In order to transport them without losing any trace evidence, the officers sealed the bottom of the vacuum cleaners somehow so that nothing fell out of the bottom or from the brushes (Crier 93). The significance of the vacuum cleaners is that they may contain trace evidence such as hair, fingernails, carpet fibers, or clothing fibers. Two suspicious stains were also found on the couple's bed sheets and were tested for blood and then tested to see if they belonged to Laci or Scott. Ultimately, these stains tested positive for blood using LMG, but DNA testing matched the stains to Scott, not Laci. All of the blood stains tested in the truck and on the bed sheets were shown to be Scott's blood (Crier 456).

Special debris-collecting equipment was used to vacuum around some tables. This was to collect any trace evidence on the floor. Some brownish-colored stains were found inside the house toward the rear exit - on the water heater door, in the door jamb, and what was thought to be a blood transfer pattern was found on the inside of the french door at the rear of the house that led to the backyard (Crier 95). Two of these spots tested negative for blood by using a presumptive test, but all samples were collected anyway. Squares of the carpets were clipped as evidence so that they could be closely examined for any blood traces such as spatter or in the event that someone cleaned the carpet to get rid of anything.

When an unidentified female body and that of a full-term fetus washed ashore along the banks of the San Francisco Bay, the bodies were in a bad state of decomposition. The female body had no skull, hands, or feet, so fingerprint identification and dental records could not be used to identify the victim. Luckily, since the waters in the bay were so cold, decomposition had been slower than normal and the female body still had pink muscle tissue (Crier 343). The fetus did not have as much decomposition or fish activity as the female body, which led coroners to believe that the fetus had been protected inside of the female's womb until recently when it was expelled in a "coffin birth". DNA samples were taken from the bone and tissue of both the female body and the fetus. The female was positively identified as Laci by comparing "DNA from the muscle and bone samples from the autopsy" to DNA samples that had been obtained from each of Laci's biological parents (Crier 351). In addition to the parents' samples, analysts were able to use hairs from a brush belonging to Laci and a recent pap smear from her gynecologist. The fetus was identified as Conner. Scott had provided a DNA sample previously, which was used in this identification - also proving that Conner was Scott's biological child since he had raised some concerns about the child's paternity to others during the investigation (Crier 351).

I believe that there were some mistakes made during the crime scene investigation. Maybe more biological or DNA evidence could have been found. There was a mop bucket that Scott had supposedly dumped water from upon returning home to find Laci missing that could have been tested for traces of blood - if he was mopping blood from the floor or attempting to clean up any other evidence. Dirty clothes were viewed in the hamper but never collected. Also, a tarp thought to conceal Laci's body while he supposedly drove her to Berkeley Marina could have been tested for trace evidence such as blood, saliva, amniotic fluid (if injury was caused to the placenta thereby causing leakage), clothing fibers that may have been consistent with what Laci was wearing, and hairs. Some animal hairs (cat and dog) were collected from one of the tarps, but the dog hair was not consistent with McKenzie, the couple's dog (Crier 322). Also, the large umbrellas that were in the back of Scott's truck could have been collected and tested since Scott supposedly, according to the prosecution, had placed Laci's body alongside them in the back of the truck. Any trace evidence belonging to Laci that was found on these umbrellas would have been important to the case against Scott. The fact that a hair was found on some pliers in his boat at the warehouse was significant. Even if she had visited the warehouse a few days before her disappearance, how would her hair become stuck to or in between the pliers? The washing machine should also have been tested for the presence of blood. Since the first thing that Scott did when he returned home on Christmas Eve was to wash his clothes and shower. Traces of blood or other evidence could have been found or detected.

In my opinion, since none of Laci's blood was found in her home or in Scott's vehicle or boat, Laci was asphyxiated. Other investigators also believe she was given the "silent death" by strangulation or asphyxiation. I believe that Laci could have been asleep or knocked unconscious and someone held a pillow over her face to suffocate her. I could not understand why investigators collected the sheets and duvet cover from the couple's bed but not the pillows or pillow cases. Why wouldn't you collect it all? I never saw any mention of the pillows or pillow cases being collected. If the pillows were collected and processed, I would think that if they were used to suffocate Laci, there may be evidence of tears from her eyes, or saliva, or bite impressions from her mouth as she struggled to gasp for air under the pillow. Investigator's were also very intrigued by an indentation they saw at the foot of the bed in the duvet cover, but I don't think it was of any significance. Investigators believe that the indentation was the perfect size for a body, but if the mark was made by Laci's body wouldn't there have been other indentations on the duvet comforter caused by Scott supposedly pulling her or lifting her 152 pound body from the bed? I have a duvet comforter and indentations are left like that when I lie down on top and get straight back up. I feel that Scott must have laid down on the comforter or rested his jeans, his robe, or an item of clothing on this comforter to cause the indentation. This might make sense since he took a shower almost immediately upon returning home. The autopsy report also noted that Laci had three broken ribs (Crier 465). One investigator claimed the breaks could have been consistent with a kick in the chest or side of the body (Crier 339). This could have been what initially immobilized Laci so that Scott could take control and suffocate her or she could have been kicked afterwards as he was strugling with her lifeless body during the transportation to the marina. Interestingly enough in this case, I don't think DNA played a huge role in convicting Scott except for the identification of the bodies.

Here are my current-day thoughts:

I believe Scott was wrongfully convicted. Whether he is innocent or not, there was not any evidence - it was only circumstantial. Yes, he was a cheater, and yes he was a crappy husband, but that doesn't make him a killer. Just like the West Memphis 3 (I keep referencing this because I went down the rabbit hole last week, so it's still fresh) - yes, they wore black and listened to Metallica, but that doesn't make them killers. I've read several books on the Scott and Laci case, and there should have been reasonable doubt. I actually follow the Scott Peterson is Innocent page on Facebook, and here is the link if you would like to check it out. Scott Peterson is Innocent Facebook Group

This is a controversial topic for some people, so please do not leave rude comments on my page. This is my opinion.

Works Cited:

Crier, Catherine with Thompson, Cole. A Deadly Game. New York: HarperCollins Pulishers Inc., 2005.