Deciphering RNA to solve impossible crime scenes

Attempting to decipher numerous pieces of evidence at crime scenes presents a multitude of questions. Who was stabbed, and what type of tissue is on the knife? Which gun fired each bullet and what organs did they pass through causing the fatal injury? Whose finger pulled the trigger?

A modern-day “whodunit” is unraveled in a brightly lit laboratory that serves as the 21st century version of crime-fighting headquarters; the Netherlands Forensic Institute (NFI) which hosts a staff of 500 professionals, sharing expertise in over 30 fields, and delivering 60,000 forensic services a year. At the heart of the NFI are two forensic scientists who search for microscopic evidence finding ‘the how and the who’ behind each crime. A dynamic duo, Dr. Titia Sijen, research team leader of the biological traces division, and Dr. Margreet van den Berge, research scientist, focus on DNA and RNA analyses to find answers to some tragic questions.

Crime scenes are often far from pristine or straight forward. Most recently, an event occurred involving multiple shooters, with multiple bullets fired. “Forensic science is challenging. Samples are often degraded, low quality and quantity, and contain contaminants that can interfere with the data,” van den Berge notes. “But as challenging as forensic science is, it is also incredibly informative, with every touch leaving a trace.”

RNA – the next step in forensic research

Using DNA to connect an individual to a crime is well known; however, the forensic team at NFI is using RNA to glean more detailed information about crimes from evidence collected at the scene.

“I like working with RNA. RNA was previously considered to be unusable from a forensic standpoint, because it degraded too quickly. But we now know that tiny snippets of RNA can be extremely longlived,” explains Sijen. “Even in 20-year-old dried blood samples, and bodies excavated after four to 44 years, we can find RNA of a quantity and quality that can be analyzed. When people think of forensic science they tend to think of DNA and its use in matching a suspect to a crime scene. Because RNA represents the genes that are expressed in a cell (the transcriptome), and differs between cell types, it can tell us things that DNA can’t – such as which body tissue or fluid is present at a crime scene. If we’re working to solve rape cases, we may assess the presence of body fluids like vaginal mucosa on male samplings. In murder cases, where we need to work out which shot is fatal for example, we focus on identifying which organs a bullet passed through.”

In 2019 van den Berge was awarded the QIAGEN Young Investigator Award for a research study investigating single nucleotide polymorphism (SNP) mutations in messenger RNA (mRNA) fragments to link cell-types and donors. “We can identify different organs and body fluids as well as identify what person those samples originated from,” van den Berge says. “In the case of the three shooters, we were able to determine who fired each bullet by working out which bullet originated from which weapon,” explains van den Berge. “A molecular analysis of the RNA from tissue fragments adhering to the bullets allowed us to assign the tissue to a specific organ because each organ exhibits a unique pattern of gene expression. In this way we could say whether a bullet passed through, for example, the brain or the heart.”

The team use QIAGEN Multiplex PCR kits that require RNA strands of less than 150 nucleotides to detect biomarkers for different body fluids and organs, and to date have carried out RNA profiling in more than 300 cases.

A forensic science partner

Sijen believes the highly specialized field of forensic science greatly benefits from collaboration. “Working with other researchers and commercial partners like QIAGEN will lead to a greater impact, new technology, and more forensic cases solved. The QIAGEN extraction kits are excellent for forensic work because they give us good quality RNA, overcoming our challenges of small sample size and significant contamination.”

A self-professed science nerd, Sijen enjoys the contemplation and analysis aspect of forensic science. “Finding the truth has a social relevance that is important to me.”

“I think RNA SNPs are really the next step in forensic research,” says van den Berge, “and I think that's fascinating.”