Systematic study for DNA recovery and profiling from common IED substrates: From laboratory to casework

Area of Science:

• Forensic Science
• Molecular Biology
• Trace Evidence Analysis

Background:

• Improvised explosive devices (IEDs) are frequently used in terrorist attacks globally.
• Trace DNA evidence left during IED assembly is often degraded by deflagration.
• Efficient DNA recovery methods are critical for forensic investigations involving IEDs.

Purpose of the Study:

• To systematically evaluate and identify optimal DNA collection methods for trace DNA on IED components.
• To validate the most effective DNA collection techniques using actual IED casework evidence.
• To improve standard operating protocols for DNA recovery in forensic casework.

Main Methods:

• Six swab types and six moistening agents were tested on dried buffy coat stains across four common IED substrates.
• Collection efficiencies were compared between optimized swab/moistening combinations, tape-lifting, and direct DNA extraction.
• A post-study protocol was developed and validated on 195 pieces of IED evidence, comparing it to pre-study methods.

Main Results:

• No single swab or moistening agent was universally superior; swab type had the greatest impact on DNA recovery.
• Moistening agents, substrates, and their interactions significantly influenced DNA recovery percentages.
• Optimized swab/moistening combinations performed comparably to the best tape-lifting and direct extraction methods.
• The post-study protocol led to a significant improvement in short tandem repeat (STR) profiles from IED evidence.

Conclusions:

• The study provides a validated protocol for maximizing trace DNA recovery from IED evidence.
• Continuous re-evaluation of standard operating procedures using empirical data is essential for forensic science.
• Optimized DNA collection methods enhance the quality and quantity of genetic profiles obtained from challenging forensic samples.