Michelle Hill, QIMR Berghofer Medical Research Institute, and The University of Queensland, Australia
Popularized by crime scene investigation dramas, forensic DNA technology is widely known to the public. The potential for using human DNA fingerprinting in forensic science was first reported by Professor Alec Jeffreys in 1985. By matching incriminating genetic material to DNA fingerprints from suspects (or a database), it’s possible to surmise “who” may or may not have been present at the crime scene. The same DNA fingerprinting technology has since been commercialised for ancestry tracing and parentage confirmation.
While DNA profiling has helped to solve the question of “who” in crime investigations, it has no or limited power to enlighten on the “what” or “how” of a crime. But never fear, the new super power protein profiling is here!!
The scientific term for protein profiling is “proteomics”, which is used to describe large scale analysis of known or unknown proteins. For unknown mixtures of proteins, such as that encountered in forensic investigations, the technique of mass spectrometry (shortened to MS) is used along with DNA sequence databases to compute the protein identities. The recent advances in MS and gene sequencing technologies have given birth to a new super power - forensic proteomics.
In Italy, the super power of forensic proteomics has been pioneered by Dr Gianluca Picariello (Institute Food Sciences at National Research Council of Italy) upon input of the forensic toxicologist Dr Maria Pieri (Legal Medicine Section of University of Naples). Normally, Gianluca’s research laboratory applies proteomics technique in the investigation of food composition and evolution, so he is used to analysing partly digested food of varying stage of decay. These skills became super powers to help Maria determine the truth of statements from persons of interest in 2 different criminal cases.
In the first case on the death of a mental health patient at a clinic, there was a discrepant account on whether the victim had eaten breakfast. The usual forensic methods of visual investigation of the gastric content at autopsy could not answer this question, even when examined under the microscope. Gianluca’s forensic proteomics super power provide unequivocal evidence that the victim had eaten recently milk and baked wheat food, consistently with a typical Italian breakfast. The inconsistency between evidence and declaration of the attending sanitary staff, prompted Legal Authority to undertake further investigations to ascertain facts and possible responsibilities.
Secondly, in rape case, the investigators had to determine whether traces of biological material was vomit. DNA profiling was not helpful because the dispute was whether the victim gave consent, or had vomited and fainted, and therefore could not have consented. The problem is, the car had been washed since the incident, leaving scant traces of biological material which could not be analysed by standard forensic methods. Once again, Gianluca’s super power easily provided the answers, identifying human proteins from saliva, stomach and intestine, in addition to food proteins. “Data were clearly indicative of vomit, thereby supporting consistence between victim's report and facts.”, said Gianluca.
The forensic proteomics super power was fuelled by Gianluca’s research, which has established marker proteins for different food types. Furthermore, his previous work with Professor Francesco Addeo of University of Naples on the dynamics of food degradation provided the knowledge to reconstruct the meal composition from the puzzle of the fragments of partially digested food. While these two cases demonstrate the power of ad hoc food proteomics in forensic science, the full super power of forensic proteomics can only be unleashed after establishing validated methods and reference standards. This is exactly what Dr Eric Merkley and colleagues Drs. Kristin Jarman and Karen Wahl at Pacific Northwest National Laboratory (PNNL), Washington, USA, has been doing, on the other side of the globe.
PNNL was tasked by US Department of Homeland Security to develop guidelines for the National Bioforensics Analysis Center to use in the analysis of ricin, a deadly biological toxin that had been used in several murders.
As Eric explains, “Ricin is toxic because it enzymatically degrades ribosomes and shuts down protein synthesis. The proteomics approach complements and confirms results from existing biochemical assays, which have some limitations.”
To meet the specific and stringent requirements for admissible scientific evidence in the U.S. Federal court system, the PNNL team had to establish rigorous statistical and scientific methods for forensic proteomics. To this end, the efforts of Human Proteome Organisation in standardising mass spectrometry data reporting was appreciated by the PNNL team, who consulted the Human Proteome Project Mass Spectrometry Data Interpretation Guidelines 2.1, along with standards documents from the World Anti-Doping Organization and the Organization for the Prevention of Chemical Weapons.
PNNL’s effort in standardising proteomics analysis of ricin has allowed this super power to be routinely used in criminal case work to provide support previous methods. Clearly, the super power of forensic proteomics is beginning to emerge in different parts of globe!
To unleash the super power of proteomics, international standardization efforts are critical to establish proteomics as a rigorous scientific method that can progress beyond “research-only” to “application-ready” technology. This has been one of the objectives of the Human Proteome Organisation (HUPO), to cultivate more proteomics super powers.
Interested to know more? Read Gianluca and Maria’s detective work in their scientific articles published in Journal of Proteome Research and Journal of Proteomics. A new book edited by Dr Eric Merkley “Applications in Forensic Proteomics: Protein Identification and Profiling” published by The American Chemical Society provides an overview of proteomics in human body fluids, bone and microbial samples, as well as identification of toxins and considerations of accreditation and defensibility of proteomics evidence.