Mass-Spectrometry-Based Proteomics Reveals Organ-Specific Expression Patterns To Be Used as Forensic Evidence

Standard
forensic procedures to examine bullets after an exchange
of fire include a mechanical or ballistic reconstruction of the event.
While this is routine to identify which projectile hit a subject by
DNA analysis of biological material on the surface of the projectile,
it is rather difficult to determine which projectile caused the lethal
injuryoften the crucial point with regard to legal proceedings.
With respect to fundamental law it is the duty of the public authority
to make every endeavor to solve every homicide case. To improve forensic
examinations, we present a forensic proteomic method to investigate
biological material from a projectile’s surface and determine
the tissues traversed by it. To obtain a range of relevant samples,
different major bovine organs were penetrated with projectiles experimentally.
After tryptic “on-surface” digestion, mass-spectrometry-based
proteome analysis, and statistical data analysis, we were able to
achieve a cross-validated organ classification accuracy of >99%.
Different
types of anticipated external variables exhibited no prominent influence
on the findings. In addition, shooting experiments were performed
to validate the results. Finally, we show that these concepts could
be applied to a real case of murder to substantially improve the forensic
reconstruction.