Rain Did Not Wash Away Defendant’s Blood and DNA in Trayvon Martin Murder Case

January 6, 2013

Absence of evidence is not evidence of absence.

The defendant claims that Trayvon Martin punched him repeatedly in the face (24 times) after breaking his nose and knocking him to the ground with a sucker punch. He told the police that Trayvon straddled him as he lay on his back and rained down blow after blow striking him in the nose and face approximately 24 times. When he started screaming for help, Trayvon then grabbed his head and started slamming it into a cement sidewalk until he thought his head would explode. Then Trayvon pinched his nose and covered his mouth to silence his screams for help and suffocate him to death. He said he suddenly remembered that he had a gun concealed in a holster inside the waistband of his pants behind his right hip when he thought he felt Trayvon reaching for it, so he pulled it out, extended his right arm and shot Trayvon to death.

There are a multitude of problems with this story, not the least of which is the absence of any significant wounds that one would expect to see from such a beating. We have examined and discussed photos of the defendant’s wounds taken by a professional photographer at the police station several hours after the shooting and concluded that his minor wounds are not consistent with his story. We have several medical professionals commenting on this blog who have treated patients who were beaten as badly as the defendant claimed he was beaten and their wounds were far more serious than the defendant’s and required medical treatment. The defendant was treated at the scene and declined multiple offers to transport him to the ER for treatment. The photos taken at the police department do not support his claim that his nose was broken. In fact, we have not found any persuasive evidence that Trayvon ever struck the defendant.

For example, if the defendant’s story were true, we would expect that the crime lab would have detected the presence of the defendant’s blood and DNA on the lower sleeves and cuffs of his two sweatshirts and his fingernail cuttings obtained by the Assistant Medical Examiner at the autopsy. The crime lab did not detect the presence of blood on the lower sleeves and cuffs of Trayvon’s sweatshirts and the only DNA detected in the fingernail cuttings excluded the defendant and was was consistent with Trayvon Martin.

The defendant’s supporters contend that no blood was detected on the cuffs and lower sleeves of Trayvon Martin’s two sweatshirts because the rain had washed away all of the defendant’s blood and the scrapings from only one fingernail were tested. They also claim that no blood was discovered on Trayvon’s hands because Trayvon covered them with plastic bags before he assaulted the defendant.

Let’s deal with the last claim first because it is the most ridiculous. Police routinely bag the hands of homicide victims to preserve trace evidence and that is what they did to Trayvon’s hands.

They also complain that Trayvon’s hands were not swabbed, but that is not surprising since the standard practice is to cut a homicide victim’s fingernails and examine them for trace evidence. Forensic scientists do this because trace evidence can transfer from a victim’s hands to another person, surface or fall off. Trace evidence, particularly blood and DNA gets trapped under fingernails and that is why fingernail cuttings are the preferred location to check for trace evidence.

They soak the fingernail cuttings in a solution of purified water overnight and spin it out in a centrifuge to obtain all of the cellular debris present. Then they examine the debris under a microscope. If they find intact cells, the extract the DNA and type it. They do not scrape one fingernail and throw the rest away. Whoever conjured up that explanation has absolutely no idea what they are talking about. It’s probably the same person who said Trayvon wrapped his hands in plastic bags before assaulting the defendant.

Pathetic and laughable nonsense.

What about the claim that rain washed away the blood and DNA?

That claim is almost, if not quite as ridiculous, because we are discussing whether the rain would wash away all blood present on fabric leaving no detectable trace amount. To understand why the rain would not wash away any detectable amount of blood, let us take a look at presumptive tests for blood and failed efforts to remove all detectable trace amounts of blood invisible to the human eye.

Experience has shown that it’s virtually impossible to clean-up blood spatter at a crime scene so that no DNA can be detected. And that is after using water, solvents, cleaning fluids and other assorted chemicals in multiple washings to remove all visible traces of blood. Even though the human eye cannot see trace amounts of blood residue, luminol will detect it. Luminol is so sensitive that it can detect the presence of blood in serial dilutions down to 1:100,000. If luminol can detect it, PCR testing certainly will type the DNA present.

Other chemicals used in presumptive testing for the presence of blood are leuchomalachite green, phenolphthalein, Hemastixs, Hemident, and Bluestarr. All are as equally sensitive to blood as Luminol except for leuchomalachite green (1:10,000). For more information, please read this Technical Note in the Journal of Forensic Science, published in 2006. JFS is a peer reviewed professional journal.

The defendant’s supporters do not realize that a complete DNA profile can be developed from the DNA contained in a single white blood cell by using the STR/PCR process (red blood cells do not have a nucleus). In practice, they require more than a single cell to avoid copying a contaminant DNA introduced extraneously into the testing process, but they do not need very much sample.

In the mid 80s, Dr. Kary Mullis developed a new DNA typing system that involved using chemicals and bacteria present in high temperature hot springs to mimmick cellular division and create more DNA, or PCR product to type. PCR is short for the polymerase chain reaction. The process can produce millions of copies of specific sequences of genetic material or loci called STR’s (short tandem repeats) The FBI Crime Lab later standardized the DNA extraction and typing process. By the end of the 90s, all public and private crime labs were using the same kit to type DNA and that is what the Florida Crime Lab did in this case.

In 1993, Dr. Mullis was awarded the Nobel Prize in Chemistry for his discovery.

Therefore, the argument that rain washed away even invisible trace amounts of blood and DNA is ridiculous and not supported in any of the peer reviewed literature.

For more information on Dr. Mullis, please visit his website and Wikipedia. He is a genius, avid surfer and fascinating character, even if some of his political views and opinions are a bit odd.


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