Determining the source of equine bloodstains by dinucleotide repeats.

The research paper presents a case study that used a unique system of identifying horse DNA to track the source of equine blood found at a crime scene.

Objective of the Study

The research primarily focuses on determining the source of horse blood using a novel multiplex of independent dinucleotide tandem repeat (DTR) loci. This system is capable of distinguishing human DNA from equine DNA and identifying a single source of horse DNA.

The Case Study

• The setting of the study involves a barn that was inspected by the Pennsylvania Racing Commissions. A bloodstained syringe and two needles were found at the scene.
• The suspects for the source of the blood included a range of horses, one of which was identified as a potential source. The suspected horse was examined for the 21 equine DTR markers, which are specific segments of DNA that can be tracked.
• All 21 equine DTR markers were found in the suspect horse and two of the evidence samples, suggesting that these samples had come from the suspected horse.

Limitations and Findings

• Only six of the markers were detected in the third piece of evidence, which could be due to the sample having a limited volume of blood.
• In order to extract more information, the researchers performed a whole-genome amplification and single-locus PCR, which is a method of making multiple copies of a specific piece of DNA. This process detected a total of 17 markers from the third sample.
• The probability of the third sample belonging to the suspect horse (as opposed to a random horse of the same breed) was calculated to be 7.0 × 10⁶, a likelihood that significantly implicates the suspect horse as the source.
• Although the process has some technical limitations, the researchers conclude that this DTR multiplex method is already practical for use in investigations concerning equine blood samples.