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Author Spotlight: Advancing DNA Extraction from Necrophilic Fly Samples using Simple Technique
Published on: May 3, 2024
The use of forensic tests to distinguish blowfly artifacts from human blood, semen, and saliva
Annalisa Durdle1, R John Mitchell, Roland A H van Oorschot
1Department of Genetics, School of Molecular Sciences, La Trobe University, Melbourne, Vic., 3086, Australia; Biology Division, Victoria Police Forensic Services Department, Macleod, Melbourne, Vic., 3085, Australia.
Abstract:
This study investigated whether routinely used forensic tests can distinguish 3-day-old or 2-week-old fly artifacts, produced after feeding on human blood, semen, or saliva, from the biological fluid. Hemastix(®) , Hemident(™) , and Hemascein(™) were unable to distinguish blood from artifacts. Hemastix(®) returned false positives from negative controls. ABAcard(®) Hematrace(®) and Hexagon OBTI could distinguish blood from 3-day-old artifacts, but not 2-week-old artifacts. Phadebas(®) and SALIgAE(®) were unable to distinguish saliva from artifacts. RSID(™) -Saliva was able to distinguish saliva from 3-day-old artifacts, but not 2-week-old artifacts. Semen tests Seminal Acid Phosphatase, RSID(™) -Semen, and ABAcard(®) p30 were all able to distinguish semen from 3-day-old artifacts, but not 2-week-old artifacts. The tests investigated cannot be relied upon to distinguish artifacts from biological fluids. However, if an artifact is identified by its morphology, a positive result may indicate which biological fluid the fly consumed, and this knowledge may prove useful for investigators searching for DNA.
Insights
Forensic tests struggle to differentiate aged fly artifacts from biological fluids like blood, semen, or saliva. While some tests identify fresh artifacts, older ones often yield unreliable results for forensic casework.
Area of Science:
- Forensic Science
- Biochemistry
- Entomology
Background:
- Forensic investigations often encounter biological samples contaminated with insect artifacts.
- Distinguishing between genuine biological fluids and aged fly artifacts is crucial for accurate analysis.
- The reliability of common forensic tests on aged biological samples remains a significant challenge.
Purpose of the Study:
- To evaluate the efficacy of standard forensic tests in distinguishing aged fly artifacts from human blood, semen, and saliva.
- To determine the limitations of these tests when applied to samples of varying ages (3 days vs. 2 weeks).
Main Methods:
- Fly artifacts were generated after feeding on human blood, semen, and saliva.
- Artifacts were aged for 3 days and 2 weeks.
- Routine forensic tests (Hemastix, Hemident, Hemascein, ABAcard Hematrace, Hexagon OBTI, Phadebas, SALIgAE, RSID-Saliva, Seminal Acid Phosphatase, RSID-Semen, ABAcard p30) were used to analyze the artifacts and compare them to fresh biological fluids.
Main Results:
- Most tested forensic kits failed to reliably distinguish between aged fly artifacts and the original biological fluids.
- Some tests showed limited success with 3-day-old artifacts but failed with 2-week-old samples.
- False positives were observed with some tests on negative controls.
Conclusions:
- Current forensic tests are not dependable for distinguishing aged fly artifacts from biological fluids.
- Morphological identification of artifacts is essential.
- Positive test results on morphologically identified artifacts may still indicate the consumed biological fluid, aiding DNA investigation.
