Cold Case Unit Tools & Methodologies

The Combined DNA Index System is a meeting of computer and forensic science with a higher purpose: CODIS combs through massive numbers of DNA profiles looking for matches that will help solve violent crimes. The system is based on a national database of DNA profiles collected from crime scene evidence and people convicted of felony charges. (Some states also include DNA from people arrested in felony cases.)

Every night, CODIS searches for DNA matches of all of the profiles in its database, be they between a convicted person and a crime scene or just between crime scenes. That’s how agents can see, for example, that a person likely committed multiple murders or sexual assaults, even if agents can’t identify who that criminal is yet.

When the system finds a link, BCI is notified. These links are leads, which means they require that a law enforcement agency investigate further. That work can involve examining circumstantial evidence to see whether the person could have committed the crime. It also can involve obtaining a warrant to swab the person for a DNA sample, which is submitted to the crime lab for a direct comparison to the case evidence. 

Ohio joined the FBI-supported CODIS in the late 1990s. Today, all 50 states upload DNA profiles to the system, with Ohio adding about 4,000 per month. The same locations on the DNA strands are required to be tested and uploaded to the national system. That uniformity allows, for example, a DNA profile from a 1999 case to be compared to a current DNA case.

On occasions when CODIS links DNA between crime scenes but can’t link it to a known person’s profile in the system, further analysis can find DNA in the database that is similar and could come from a family member of the perpetrator. This is known as familial DNA testing.

When BCI conducts such tests, using a special software that searches DNA samples in the CODIS database, they are more expensive and used only in certain cases. If potential matches are found, scientists take a look at at one chromosome, the Y chromosome, which is inherited in male lineages. Every male’s Y chromosome exactly matches his father’s, paternal grandfather’s and those of any brothers and sons he has. 

When a Y chromosome from crime scene evidence matches a known person’s Y chromosome from that CODIS search, Criminal Intelligence analysts go to work establishing the family tree of the known person. They research whether any of the person’s same-sex relatives could have committed the crime, including whether the relative would have been old enough (or young enough) and whether the relative was known to have been in the area when the crime occurred.

If such a person is located, further DNA testing is used to confirm that the crime scene DNA does, in fact, match that person's DNA.

Here’s the story of a BCI cold-case investigation where familial DNA testing led to a suspected serial killer.

BCI is partnering with the Battelle Memorial Institute to validate and implement massively parallel sequencing-based (MPS) testing of mitochondrial DNA (mtDNA).

MPS differs from traditional DNA testing by allowing for numerous samples and DNA targets to be sequenced simultaneously, which translates to more information being obtained from a greater number of samples in a shorter timeframe than ever before.

BCI is one of the first state crime labs to implement MPS-based mtDNA testing and will be using this new tool exclusively for Project LINK casework.
 
mtDNA offers numerous benefits in cases that otherwise have gone cold or in which all other types of DNA testing have been exhausted. 

Traditional DNA testing performed at BCI requires nuclear DNA to be present. Nuclear DNA is a fragile molecule with only two copies per human cell. In cases where samples are old or have been potentially damaged by environmental factors, nuclear DNA can be broken down and successful testing impossible. In contrast to nuclear DNA, mtDNA is a robust molecule with 100 to 10,000 copies per human cell. In extreme cases where nuclear DNA is degraded, there is a very good chance that larger numbers of intact mtDNA are available for testing. The MPS-based mtDNA testing at BCI takes advantage of this robust and plentiful molecule to generate new information for old cases.

In contrast to the previously described Familial DNA testing, which is based on paternal (male) lineages, mtDNA is maternally inherited. This means that each individual in a particular maternal lineage will have the same mtDNA profile. Therefore, if an mtDNA profile from a missing person or unidentified human remains is obtained, any individual from the mother’s side of the family could be used to make a connection between that family and the remains. Even distant maternal family references can be used in cases where direct references are unavailable.

It is important to remember that mtDNA testing is maternal lineage-based. Similar to the paternal lineage-based Familial DNA testing,  any mtDNA-based match is not a unique identifier and must be considered alongside other forensic and investigative information.      

The Cold Case Unit and the lab are working to notify agencies of thousands of older sexual assault cases in which new technological advancements could mean new leads.

For cases in which a DNA profile was developed from one of the 13,931 sexual assault evidence kits previously tested (part of this testing initiative), the Cold Case Unit and the lab are going back to the original agencies to alert them that additional investigative or laboratory strategies could make a difference in bringing the perpetrator to justice.

• Provides analysis of digital forensics, cellphone records, geolocational resources, social media posts, family links, etc.
• Creates case timelines, databases of evidence and people relevant to the case, visual aids such as crime scene maps, facial reconstructions
• Operates the Ohio Unsolved Homicides database, the Ohio Missing Persons database and the Unidentified Remains database
• Helps draw media attention and promotion of cases to generate new tips and information

The Criminal Intelligence Unit also plays a big role in Project LINK (Linking Individuals Not Known), which gathers photos, DNA and other identifying information in cases of missing people. In fact, coroners in the state are required to send BCI a DNA specimen from any bodies that go unidentified for 30 days. This information is added to various databases in the hopes of identifying people whose remains have been found at crime scenes or in potentially suspicious circumstances — and in the hopes of providing family members with answers about what happened to their loved ones.

A trained forensic artist at BCI specializes in combining art and science to help identify suspects and missing persons. Some of the applications:

• Composite imagery, which can generate leads in locating a person of interest in a missing person investigation, is the process of creating an image through cognitive interviews of witnesses.
• Image modification can be used to create postmortem or age progression images. Postmortem imaging converts an autopsy photo into an image of what the person may have looked like when alive, to generate tips that assist in identification. An age progression is utilized years after a person went missing. The forensic artist modifies the image of the person to resemble what he or she may look like now.
  • See examples of postmortem images in this case and this one, which has been solved.
  • See examples of age progression images here and here.
• Facial reconstruction can be used for cases where an unknown person’s skull has been found. One process the artist uses starts with a CT scan made of the skull at a local hospital. The scan is converted to a 3-D image that is then 3-D printed, producing an exact replica of the skull. The replica is used to create an image or a clay model of what the person looked like, which can be forwarded to law enforcement and the news media to generate tips. The process also preserves the remains and any evidence that might be left behind.
  • See the process here. (The page takes a few extra moments to load.)

Familial DNA testing and Investigative Genetic Genealogy searches do not identify the perpetrator whose DNA was collected from a crime scene or victim. However, both approaches may be useful in identifying a relative of the perpetrator.

After Genetic Genealogy evidence testing, Criminal Intelligence analysts enter the resulting DNA profiles into publicly available open-data DNA databases or direct-to-consumer genealogy services. Both types contain the genetic profiles of people who have voluntarily submitted DNA samples or entered their genetic profiles into the services.

If the process results in a hit — that would be a potential family member of the perpetrator — analysts will thoroughly research the individual’s family tree to evaluate whether any known relative could be the perpetrator.

All leads developed from the process are confirmed by standard DNA tests to ensure the right person is caught and prosecuted.

• Interviews and interrogations
• Advanced technological strategies and electronic intercepts
• Polygraphs
• Crime scene reconstruction
• Gunshot trajectory
• Bloodstain pattern analysis
• Digital and cyber forensics
• Victims advocacy
• Exhumations/clandestine graves