How DNA testing will be used in the case against Craig Michael Wood

February 22, 2014

Saturday, February 22, 2014

Good afternoon:

I have received several emails asking me repost as a separate post my comments yesterday about DNA testing in the Craig Michael Wood case.

Here they are with some grammatical changes to promote clarity:

I suspect Wood may have committed a sex crime, since I do not believe he kidnapped Hailey for the sole purpose of killing her.

The ligature marks on her arms and the child pornography seized by the police during the search at his residence suggest he may have committed a sex crime.

I also suspect he may be a serial killer, even though he supposedly does not fit the profile. My suspicion is based on the brazen kidnapping in front of witnesses and the speed with which he committed the crimes, cleaned up the crime scene and prepared to dispose of Hailey Owens’s body. But for the lack of duct tape, he might have gotten away with her body and disposed of it before police arrived at his house. That would have complicated and possibly prevented a successful prosecution.

Whether I am right or wrong will have to await the results of the investigation and forensic DNA testing.

Meanwhile, I can describe the forensic DNA testing that will take place so that everyone understands the procedure and how it works.

During the autopsy, the medical examiner likely swabbed her mouth, anus and vagina separately using sterile swabs, packaging each swab separately and securely so that no foreign DNA could contaminate any of the swabs. They would have been submitted to the DNA lab together with a dried bloodstain obtained from her blood at the autopsy to develop a DNA profile from a known individual to use as a reference sample for comparison purposes.

A DNA analyst should be able to obtain a complete DNA profile from a small cutting obtained from the dried bloodstain (13 genetic sites, plus a sex determinant).

The analyst will take a cutting from each swab and place each one in a separate test tube containing a small amount of distilled water. After soaking the swabs for a certain period of time to allow the dried biological fluid on each swab to go into solution, the analyst will remove the cuttings and spin the test tubes to collect any biological substances present at the bottom of each tube.

After pouring off the solution, the analyst will place a portion of the residue from each tube on separate microscope slides and examine each slide for the presence of spermatozoa and female epithelial cells.

Epithelial cells come from the lining of the vagina, anus or mouth and slough off during intercourse.

By using a process called differential extraction, the DNA in each sample that contains spermatozoa and epithelial cells, assuming they are present, will be selectively released by first adding a mild chemical that breaks down the wall of the nucleus of every epithelial cell releasing the DNA into solution.

The chemical is not strong enough to break down the nucleus of a sperm head and release the male DNA.

After the female DNA is extracted from the epithelial cells, the male DNA is released into solution by adding a stronger chemical.

The analyst will then use the polymerase chain reaction (PCR), which is the biochemical process developed by Dr. Kary Mullis in 1983 to create millions of copies of a particular DNA sequence of interest.

This process is applied to the extracted DNA enabling easy typing of the sequence of interest from a biological sample containing DNA from just a few cells.

By using a process similar to gas chromatography and mass spectrometry (GCMS), the male and female DNA can be typed and compared to the known samples obtained from Hailey Owen’s bloodstain and a buccal swab obtained from Craig Michael Wood.

The DNA profile obtained from the female epithelial cells should match the DNA profile obtained from Hailey’s bloodstain at autopsy at all 13 sites and the sex determinant, assuming complete DNA profiles are obtained from both samples. Partial profiles would be expected to match at the same sites.

The DNA profile obtained from the sperm heads or male fraction, assuming any spermatozoa are present, would likely match the DNA profile obtained from a buccal swab obtained from Mr. Wood after his arrest (which is standard operating procedure in sex crime cases.

The DNA profile obtained from a mixed sample containing both the female DNA from the epithelial cells and the male DNA from the sperm heads should contain alleles matching both known sources at each of the 13 STR/DNA genetic sites and the sex determinant should indicate a mixed sample containing DNA from at least one male and one female.

Most likely the pieces that cut out of mattresses during the search of Wood’s residence are stained with a substance that reacted positively for the presence of blood.

If so, the stains will require confirmatory testing at the crime lab.

DNA in dried bloodstains preserves virtually indefinitely. If they are human bloodstains, the DNA lab may be able to develop a complete nuclear STR/DNA profile and mitochondrial DNA profile that can be compared to the missing persons database for potential matches.

Mitochondria exist outside the nucleus of a cell. They contain DNA. Because there is only one nucleus in a cell and many mitochondria, there is substantially more DNA in the mitochondria compared to the nucleus. For this reason, mitichondrial DNA degrades (breaks down) more slowly than nuclear DNA.

Unlike a complete STR/DNA profile, which is specific to a person, mitochondrial DNA is inherited from and matches a person’s mother’s DNA.

Thus, siblings with the same mother will have identical mitochondrial DNA and all will also match the maternal grandmother.

In the cases of many missing persons, the mother, grandmother, or a sibling have provided biological samples from which a mitochondrial DNA profile was developed to potentially identify unidentified human remains.

If a mitochondrial DNA profile developed from a human bloodstain found on a mattress at Craig Wood’s residence matched a mitochondrial DNA profile from a mother, grandmother or sibling of a missing person, it would be possible to identify the missing person as the source of the bloodstain, even if the body of the missing person is never found.

I suspect, but obviously do not know, if Craig Michael Wood is a serial killer. We will have to wait and see what develops during the investigation.

From my experience as a member of the defense team representing Gary Ridgway, probably the most prolific serial killer in our nation’s history, there really is not a single profile that applies to all serial killers.

Various so-called profiling experts have stated that Wood is not a serial killer because he does not fit the profile.

I do not believe they know what they are talking about.


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