How DNA Advances Are Reshaping Investigations

Almost every day there is another headline touting the power of DNA evidence. But where is this science headed?

Several advances have boosted the accuracy of forensic DNA tests. Specifically, improved methods produce better “match statistics.” These are the numbers that indicate how much more a reference profile explains DNA evidence than does random DNA.

Identifying the Golden State Killer

When the Golden State Killer began his spree of burglaries, rapes and murders in 1974, DNA profiling had yet to be invented. Now it’s one of the tools helping authorities close long-running cold case investigations.

Forensic DNA can be generated from small samples of human saliva, allowing investigators to create a DNA profile for suspects. This is important, because direct comparisons between a known sample DNA and crime scene DNA provide the only probative evidence of a link to a crime.

But the increased sensitivity of PCR makes it possible for investigators to generate multiple DNA profiles from the same sample, and this can make it difficult to tease apart which is the correct profile for a suspect. This is why genealogical databases and family trees can help.

Identifying a Suspect in a Murder Case

Forensic DNA analysis can help identify suspects and establish guilt with a high degree of certainty. It can also exclude suspects with absolute certainty. For example, if a crime scene contains sperm, police can use DNA profiling to match the profile of a known person to the sample at the crime site.

For decades, DNA analysis has been used to solve cold cases and exonerate wrongfully convicted individuals. DNA profiling has been made even more useful thanks to advances in sample processing and database technology.

In a recent murder case, DNA evidence helped identify the suspect, who was previously unknown to police. This case illustrates the power of DNA to resolve a long-term murder case and bring closure to victim’s families. The technology is now being paired with genealogy databases to help solve more cold cases.

Identifying a Suspect in a Sexual Assault Case

The most common form of DNA evidence used to identify suspects in sex crimes involves semen samples collected from the victim’s clothing and bedding. These samples are collected by medical staff known as Sexual Assault Nurse Examiners using kits specially designed to collect the necessary forensic material while preserving the integrity of the sample.

Investigators can then use the sample to compose a DNA profile and match it to suspect records in CODIS, the FBI’s Combined DNA Index System. This has helped solve sexual assault cases and has even been instrumental in exonerating people wrongfully accused of sex crimes. It also helps prevent future cases from being perpetrated by the same person. Nilo believes it is important that forensic DNA tests are properly conducted and the proper chain of custody followed so that the full potential of this type of evidence can be realized.

Identifying a Suspect in a Homicide Case

When DNA evidence is present in a case, police are able to use it to identify suspects and build cases. However, this process can be lengthy. DNA samples are compared to DNA profiles stored in national databases. The resulting match statistics are used to determine how likely the reference profile is to explain the crime scene sample.

Police have used DNA evidence to solve murders, rapes and other crimes that occurred months, years or even decades ago. The ability to store DNA in national databases has also helped identify serial rapists who weren’t initially considered suspects.

All professionals involved in the criminal justice system need to understand DNA technology and how it works. This includes police officers who collect it, prosecutors who use it in court and victim services professionals who assist victims.

Identifying a Suspect in a Drug Case

DNA profiling is a key tool in forensic science. It has helped solve countless crimes, including some decades-old cold cases.

DNA identifies individuals by unique patterns in regions called short tandem repeats. Each person inherits these repeats from their parents, and the number of repeats differs between people.

Since it became reliably available in the 1980s, DNA evidence has made a profound impact on crime solving. In many cases, it can exclude suspects completely or establish guilt with a high degree of probability.

In addition, it can help identify serial criminals by linking DNA profiles to databases of convicted offenders. The FBI’s Combined DNA Index System, or CODIS, compares unknown DNA from crime scenes to known offender profiles to generate investigative leads.