Advancing forensic science through proteomics
For more than three decades, DNA has been considered the gold standard of forensic science. It has transformed criminal investigations, identified disaster victims, exonerated the innocent, and solved decades-old cold cases. But what happens when DNA is too damaged to analyze?
Imagine a crime scene after a fire. The victim’s body is severely burned, the biological evidence is degraded, and the DNA has fragmented beyond recognition. Does the investigation end there?
Not necessarily.
Scientists are increasingly turning to another biological molecule that is often more resilient than DNA; proteins.
Welcome to the emerging field of forensic proteomics, where proteins may provide answers when DNA can no longer do so.
What is Proteomics?
Proteomics is the large-scale study of proteins; the functional molecules that carry out nearly every biological process in living organisms. Unlike DNA, which stores genetic information, proteins are the molecules that build tissues, catalyze biochemical reactions, transport substances, and regulate cellular functions.
Every tissue in the human body contains a characteristic protein profile. Blood, saliva, semen, hair, bone, and muscle all express different proteins, creating unique molecular signatures that can be analyzed using advanced analytical techniques.
This ability forms the basis of forensic proteomics.
Why Proteins?
One of the greatest challenges in forensic science is evidence degradation. Environmental factors such as heat, humidity, ultraviolet radiation, microbial activity, and time gradually destroy DNA. Proteins, however, can remain remarkably stable under conditions where DNA has become fragmented or completely lost.
Collagen, the most abundant protein in bone, has been recovered from archaeological remains thousands of years old. Similarly, proteins have been identified in burned bones, ancient skeletal remains, hair shafts lacking roots, and highly decomposed tissues.
This remarkable stability has led forensic researchers to ask an important question:
Can proteins help solve cases when DNA fails?
Increasingly, the answer appears to be yes.
How Does Forensic Proteomics Work?
Unlike DNA profiling, forensic proteomics focuses on identifying proteins or their smaller building blocks, called peptides.
The general workflow includes:
- Collection of biological evidence
- Protein extraction from the sample
- Enzymatic digestion (commonly using trypsin) to produce peptides
- Separation using liquid chromatography (LC)
- Identification by tandem mass spectrometry (LC-MS/MS)
- Database matching to identify proteins and infer their biological origin
Instead of comparing DNA sequences, scientists compare peptide mass spectra against protein databases, allowing them to identify species, tissue type, or biological fluid with remarkable accuracy.
Where Can Proteomics Be Used in Forensics?
- Identification of Burned and Degraded Human Remains
One of the most promising applications is the analysis of burned or highly degraded skeletal remains.
While DNA may be severely damaged after exposure to high temperatures, structural proteins such as collagen often persist. Researchers have demonstrated that protein analysis can assist in identifying skeletal material and distinguishing human remains from animal bones.
- Species Identification
Illegal wildlife trade is a growing global concern. Distinguishing between elephant ivory, mammoth ivory, or protected animal tissues can sometimes be difficult using morphology alone.
Protein-based techniques can identify species-specific peptide markers, providing valuable evidence in wildlife forensic investigations, food fraud cases, and archaeological research.
- Body Fluid Identification
Traditional presumptive tests for blood or saliva may produce false positives or fail in degraded samples.
Proteomics offers a more specific alternative by detecting proteins unique to particular body fluids. Researchers have identified biomarkers for blood, semen, saliva, vaginal fluid, and menstrual blood, enabling more reliable identification of biological evidence.
- Hair Analysis Without Roots
Hair shafts often lack nuclear DNA because the cells become keratinized during growth.
Proteomic analysis of keratin proteins and other hair-specific biomarkers has shown promise for characterizing hair samples that cannot be analyzed using conventional DNA profiling.
- Estimating Age and Postmortem Changes
Scientists are investigating whether predictable changes in protein degradation can help estimate the postmortem interval (PMI). Although still under active research, protein degradation patterns may eventually complement existing methods for determining time since death.
Is This Technology Really Being Used?
Yes, but with an important distinction.
Forensic proteomics is already being applied in research and specialized laboratories, although it has not yet become a routine method in most forensic laboratories worldwide.
Several notable examples include:
- Zooarchaeology by Mass Spectrometry (ZooMS) uses collagen peptide fingerprints to identify animal species from bones and has been widely adopted in archaeology and wildlife studies.
- Researchers in Europe, the United States, and Australia have developed proteomic methods for body fluid identification using LC-MS/MS.
- Studies have demonstrated protein-based identification of burned bones, highly degraded skeletal remains, and ancient human remains where DNA recovery was limited.
- International forensic research groups are actively exploring proteomic biomarkers for wound age estimation, postmortem interval estimation, and tissue identification.
While these advances are promising, DNA profiling remains the primary method for human identification because it provides individual-level discrimination that proteins generally cannot.
Why Isn’t It Used Routinely Yet?
Like every emerging forensic technology, proteomics faces several challenges:
- High-cost instrumentation such as LC-MS/MS
- Complex bioinformatic analysis
- Lack of standardized forensic protocols
- Need for extensive validation before courtroom acceptance
- Limited forensic protein reference databases
As these challenges are addressed, forensic proteomics is expected to become an increasingly valuable complementary tool.
The Future of Forensic Biology
Rather than replacing DNA, forensic proteomics is likely to work alongside it. A future forensic laboratory may analyze DNA, proteins, metabolites, and RNA from the same sample to obtain the most comprehensive picture possible.
When DNA is intact, it will remain the preferred method for individual identification. But when DNA is degraded by fire, time, or environmental exposure, proteins may preserve crucial information that would otherwise be lost.
In forensic science, every molecule has a story to tell.
While DNA profiling continues to be the gold standard for individual identification, the growing field of forensic proteomics demonstrates that protein signatures can provide critical biological information when nucleic acid evidence is compromised or unavailable.
Disclaimer
Views expressed above are the author’s own.
