Potential for DNA loss during collection and packaging of fired cartridge cases (FFC) at a crime scene
Journal of Forensic Sciences, 2025
Authors
Journal
Journal of Forensic Sciences
Study Design
Addressed Question
comparision of methods of collection and packaging of fired cartridge cases at a crime scene to determine which combination best preserves DNA integrity and quantity
Activity Context
Category
Specifications
Variables of Interest
Stringency of Control
Number of Individuals
4
Replicates per Individual and Condition
2-5
Nucleic Acid
Bodily Origin
Depositor & Contact
Depositor Characteristics
n.a.
Criteria for Shedder Status
n.a.
Previous Activities
did not wash hands 45 minutes prior to handling the fired cartrige cases (FFCs)
Contact Scenario
4 FFCs taken from envelope 1, rubbed between the donors' hands at the same time for 30 s, then placed into envelope 2
Primary Substrate
Primary Substrate Type
metal surfaces (nickel)
Primary Substrate Material
Deposit
4 FFCs rubbed between the donors' hands at the same time for 30 s
Delay
6 days
Secondary Substrate
Secondary Substrate Type
plastic bags, gloves, envelope
Secondary Substrate Material
Secondary Substrate Contact
Transport and handling of packaged FFCs
Further Transfer
/
Sampling
Background DNA on Sampled Surface
Sampling Time
delayed
Persistence
handling of FFC packages plus 70 min drive
Sampling Method
wet and dry double swab technique
Sampling Area
FFC, inside plastic bag, outside of glove before and after handling, outside and inside of device, combination of sampling sides dependent on sampling collection methods tested, overview in results table 2 and 3
Laboratory Analysis
Extraction
DNA IQ™ System (Promega, USA)
DNA Quantification
Quantifiler™ Trio DNA Quantification Kit (Life Technologies, USA), ABIPRISM® 7500 real-time PCR instrument
Input for Profiling
0.5ng or 15µL if below 0.033ng/µL
Profiling
PowerPlex® 21 System (Promega, USA), 3500xL Genetic Analyzer (Life Technologies, USA) (1.2 kv/24 s) and GeneMapper ID-X (ThermoFisher Scientific, USA)
Reference Samples
taken from all participants
Profile Interpretation and Mixture Analysis
not done
RNA Data Interpretation
N/A
Results
DNA Quantity
check Table 2 and 3 in Results part, e.g. method 1.1: gloves before handling 0ng, gloves after handling FFCs 0-0.12ng, Envelope 0ng, FFC with DNA 0.18-1.92ng; Method 1.2: Envelope 0ng, FFC with DNA 0.35-1.26ng; Method 1.3 envelope and device 0 ng, FFC with DNA 0.24-1.5ng; method 1.4 plastic bag 0-0.12ng, FFC with DNA 0.12-0.6ng, etc.
Profile Quality
mostly partial profiles
Parameter Used for Comparison
DNA quantity, number of alleles
Summary of Results
Individual FFCs Where FCCs were packaged individually and transported in a manner resembling their handling during casework (methods 1.1–1.5), DNA was recovered from all FCCs but was not detected on the inside of any envelope or collection device (Table 2). DNA was detected on plastic but not on paper packaging, DNA was detected on the inside of all plastic bags where a device was not used (method 1.4), but not detected on any plastic bag where a device was used (Table 2). FCCs inside the device were DNA-free prior to collection and packaging and remained DNA-free when tested after the handling steps (Table 2). Multiple FFCs together Where multiple FCCs were packaged together, DNA transfer was observed from FCCs to the inside of the envelope in all cases, but no DNA transfer was detected between FCCs (Table 3). Where FCCs were collected using the device and then packaged together, no DNA transfer was observed to the inside of any device, to the packaging, or between FCCs (Table 3). DNA was detected on each of the FCCs that had been handled by a donor, while none was detected on DNA-free FCCs (Table 3). When a loose FCC containing blood was packaged with two DNA-free FCCs without and with devices, DNA was detected on all three FFCs, when no device was used and mixed results when a device was used.
Raised Questions
N/A
Cautionary Remarks
Our findings highlight the importance of avoiding contact with DNA-containing areas of FCCs during collection. Ease of DNA transfer to gloves also further highlights the importance of frequent glove changes.