Article Archive Details
Hendon Publishing

New DNA Technology for Cold Cases

DNA technology is so much a part of the language of those speaking of crime detection, it is hard to believe it was first used to solve a crime in 1986. It allows any type of organism to be identified by the examination of DNA sequences that are identical to that species.

New methods of DNA technologies are being used in exciting ways, and previously unsuitable casework samples are now able to be tested. Detectives are finding it is important to keep up with DNA technology to know when to resubmit evidence that might previously not have yielded any results or to test items that had stains that were too small or degraded originally.

Useable DNA is being obtained from smaller and more unlikely sources, and cold cases may hinge on going back through the evidence and finding overlooked material from which a sample may be obtained. A toothbrush, stamp, or bite wound can yield a usable saliva sample. Patricia Cornwell used 100-year old saliva on the back of a stamp in her quest to identify Jack the Ripper. A single drop of blood or a single hair follicle may be enough to match to a perpetrator.

Previously, the bigger the DNA sample, the better. When DNA was first used, it was necessary to obtain a much larger sample, and the sample was often used up with the older DNA testing, called RFLP or Restriction Fragment Length Polymorphism. RFLP was one of the first types of DNA analysis in forensic investigation. With newer, more efficient techniques, RFLP is no longer used because of it requiring relatively larger amounts of DNA and because samples degraded by environmental factors, such as heat or mold, did not work well with RFLP.

Short Tandem Repeat

Current DNA testing is anchored by Short Tandem Repeat (STR) technology, which is the primary type of analysis currently being used. It is part of a larger type of analysis, PCR Analysis or Polymerase chain reaction (PCR), which can make millions of exact copies of DNA from a biological sample. This DNA amplification allows DNA analysis on biological samples as small as a few skin cells. To show some perspective, with RFLP, those DNA samples would have to been about the size of a quarter. Because PCR can amplify such tiny quantities of DNA, even highly degraded samples can be analyzed.

STR technology is used to evaluate specific regions (loci) within nuclear DNA. Variability in STR regions distinguishes one DNA profile from another. The FBI uses a standard set of 13 specific STR regions for CODIS.

Suzanne Kidd is a forensic scientist and a DNA specialist. She has been with the Illinois State Police Southern Illinois Forensic Science Centre in Carbondale since 1990. She has actively been involved in closing several cold cases in the area. She is the first person outside the department to receive the Chief’s Merit Award, which she received jointly with Lieutenant Paul Echols for the arrest of serial killer Timothy Krajcir. The arrest snowballed into Krajcir being charged with nine homicides in four different states. She was able to get a DNA sample from a stain on a shirt found at the homicide scene.

Kidd pointed out that “STR testing is better accepted by the courts than RFLP because it has been standardized for CODIS, and all accredited state labs are using the same locations (loci) along the DNA strand.” Kidd also said this wide acceptance of DNA testing is a double-edged sword because prosecutors are now asking for DNA testing in many more cases. Juries expect it on all cases to make a conviction, and it is known among forensic scientists as the “CSI effect.”

She said, “I can get a DNA profile using STR with a sample the size of the point of a pin. This conserves the stain and leaves material for the defense to have the option of doing [its] own testing.” She said, “Detectives are bringing old cases in for another look, and success stories are an incentive” to look at cold cases.

Mini-STR Analysis

The odds that two people will have the same 13-loci DNA profile is about one in a billion. William Frank, DNA research coordinator at the Illinois State Police Research and Development Laboratory in Springfield, IL, said the odds may be much greater. He said it could be a larger number than even the current world population or one in quadrillions and quintillions. However, sometimes samples are so degraded that normal STR testing cannot be used.

Newer DNA technology further refining STR is on the horizon and is starting to be used in criminal cases. Mini-filer or mini-STR is being used for testing previously untestable DNA samples, and it looks at one to three loci, or locations, on the DNA strand. Being able to test for even one location at a time instead of all 13 loci on the DNA strand has allowed minute or very degraded DNA samples to yield results.

William Frank used the mini-STR testing for the first time in a criminal case in Illinois on the 1976 Kathleen McSharry rape / homicide in Carbondale, IL by testing samples obtained from fingernail clippings. Frank said, “The loci in the Mini-Filer (a commercial kit for mini-STR testing) are the same 13 used in CODIS, and the manufacturer picked the markers from already existing kits with larger fragments” that were more likely to produce results. Size is the length of the DNA strand, not the actual size of the sample itself. The scientist looks at the length of the DNA strand.

Frank said when the mini-STR kit was ready for early release, the kit was sent to him to validate, test its sensitivity, and determine how it worked on degraded samples. This allowed him to make recommendations to Illinois State Police administration on implementing new procedures and quality-control measures. He explained that when the McSharry case came up, they accepted it as a non-probative case because the suspect was already deceased and they could use it for the validation study.

Mini-STR is not yet available in Illinois, but it is being reviewed for use in cases with very degraded samples. Detectives should ask their own crime labs if it is available in their areas. The procedure will still remain largely the same because the forensic science labs will need to review the samples coming into local labs for STR testing. If mini-STR testing is not available, law enforcement laboratories may be able to refer police to accredited laboratories that are offering the service.

YSTR or Y-Chromosome Analysis

Other DNA sampling methods, such as familial testing, are used for particular kinds of samples where it is helpful to test for only male or female DNA. These are often used in sexual assault cases or missing persons cases.

ISP’s Suzanne Kidd explained that in sexual assault cases, the samples usually contain lots of female DNA evidence, and conventional DNA analysis won’t detect the male DNA if it is less than 10%. YSTR looks at the male chromosome and is mainly used for such cases. Y ignores the female DNA and only pinpoints the male DNA.

It only looks at the Y chromosome, and anyone in the male lineage will be identified. But it only discerns the lineage and does not discriminate as much as other methods. The Y chromosome is passed directly from father to son, so analysis of genetic markers traces relationships among males or can analyze biological evidence involving multiple male contributors.

John Hicks, the retired director of New York State Forensic Science, pointed out an interesting case where YSTR was used to catch a killer. Male DNA was found at the scene of one of the “Bike Path Murders” in Buffalo, NY. There was no subject to match with the DNA sample, but they were fortunate enough for someone to get a license number at another scene and locate the suspect vehicle.

The suspect / owner gave a DNA sample that showed, using YSTR, that the sample was from a close relative of the offender. Police learned that the man’s nephew had borrowed his car. They followed the nephew and confiscated his used eating utensil. Using that, they made a DNA match that identified the nephew as their suspect, and he confessed. As an added bonus, they were able to exonerate an innocent man who pleaded guilty in one of the earlier crimes. Despite his confession, he was actually not the person who had committed the crime.

Mitochondrial DNA Analysis

Mitochondrial DNA analysis (mtDNA) can be used to examine the DNA from samples that cannot be analyzed using STR. While older biological samples that lack nucleated cellular material, such as hair, bones, and teeth, cannot be analyzed with STR, they can be analyzed using mitochondrial material with mtDNA.

All children (male or female) have the same mitochondrial DNA as their mothers. This is because the mitochondria of each new embryo comes from the mother’s egg cell. Comparing the mtDNA profile of unidentified remains with the profile of a potential maternal relative can be an important technique in missing persons investigations. In the investigation of cases that have gone unsolved for many years, mtDNA is extremely valuable.

Newer DNA Tech Closes Cold Cases

Illinois has been a leader in using state-of-the-art DNA technology, and the Carbondale, IL Police can lay claim to closing multiple cold cases using this method. Lieutenant Paul Echols of the Carbondale Police has worked hard to clear the list of unsolved homicides for his department.

It was his work that started the dominoes falling on the Timothy Krajcir serial killer case to the tune of nine homicides in four different states. He worked closely with Detective Jimmy Smith of the Cape Girardeau, MO Police, who was able to close five homicide cases linked to Krajcir. After Krajcir was initially charged, Smith’s previously denied request to have two unknown hairs tested resulted in an astounding 1 in 1.498 quadrillion match to the serial killer.

Echols continued working on cold cases, re-examining the evidence and submitting evidence for analysis. Kathleen McSharry, a 24-year-old Southern Illinois University student, was found nude, sexually assaulted and stabbed on July 12, 1976. Echols was able to close the McSharry homicide by submitting degraded evidence for DNA analysis.

He had approval to use a private lab to submit evidence in the McSharry case for mini-STR testing when he was referred to William Frank at the Illinois State Police Research and Development Lab. Frank used the new mini-STR sampling to link a convicted killer, John Paul Phillips, to her murder. Skin samples from McSharry’s fingernails were linked to DNA extracted from Phillips’ femur when he was exhumed.

Phillips had been suspected of several murders and died on death row in 1993 for the strangulation and bludgeoning murder of Joan Wetherall, who was left naked in a strip pit north of Carbondale in 1981. Mini-STR testing definitively tied him to the McSharry homicide. Echols was also able to close the investigation of Theresa Clark, 23, who was found dead in January 1975 in a homicide that was the mirror image of the McSharry homicide.

It was clear that the same person committed the crimes, and Phillips had actually confessed to a cellmate in the 1980s that he had committed the McSharry and Clark murders and the Joan Wetherall killing for which he was incarcerated.

Guidelines to Best Use STR Technology

While newer technology makes it possible for smaller and more degraded DNA to provide matches in CODIS, it is important to remember the ground rules. Many rules for DNA collection and testing are the same as they have always been but are important enough to review.

Suzanne Kidd said if more than one person has used an item, it can be difficult to determine one individual profile from a mixture of three or more people. She suggested looking for items that would likely have had contact with both the victim and suspected offender but that have not likely come in contact with others. She suggested looking at places where a person would likely have touched the victim or surfaces and left some of their own DNA.

She pointed out that it is often helpful to go back and re-examine evidence that has previously been tested. She said police and crime scene people are doing a better job with evidence collection and submission, but there are basic protocols that should never be ignored.

As few people as possible should be allowed at the scene to prevent contamination of the scene by talking, touching, or sneezing. Gloves and a mask are the minimum protective equipment that should be used at the crime scene, and a lab coat or protective gear would be helpful.

DNA testing is very expensive, and the lab’s guideline is that they will test up to five stains or samples. Lab personnel will often consult with the submitting agency to determine which stains would be best suited for DNA testing. That eliminates the “kitchen sink” approach when officers might bring in everything they have and hope that something provides a lead.

Frank pointed out that appropriate handling, such as keeping samples cool and dry, and storage are important because DNA samples dried and kept at room temperature are relatively stable. He said the best idea for mini-STR is “keeping the focus on degraded samples” and considering submitting the samples for mini-STR testing because the sample cannot be tested with other means.

John Hicks, a retired NY forensic scientist, said, “It is important to sit down with your local crime lab and talk them through your evidence and find the items that might show promise” to submit to the lab for testing. He said that knowing the evidence in criminal cases is very important.

The key factors to successfully closing cases using DNA samples are communication and a team approach. Detectives and other officers collect evidence, store it properly, and must keep up with advances to know when to consider resubmitting evidence. Forensic science laboratories provide consultation and advice on what to submit and when new methods might be used for certain evidence.

Kathy Marks has been a child abuse investigator for more than 25 years. She does freelance law enforcement writing and teaches law enforcement classes. She is the author of “Faces of Right Wing Extremism.” She can be reached at

Published in Law and Order, Jun 2009

Rating : 10.0

Related Products



No Comments

Article Images

Click to enlarge images.

Close ...