DNA alloys: The enduring story of touch DNA on metals
Forensic Science International: Genetics, 2026
Authors
Journal
Forensic Science International: Genetics
Study Design
Addressed Question
We report on the use of a DNA binding dye, Diamond Dye to record the presence of cellular material deposited onto a range of metallic substrates to monitor cell persistence over a 4-week period. How does a metal surface influene the downstream dna analysis?
Activity Context
Category
Specifications
Variables of Interest
Stringency of Control
Number of Individuals
1
Replicates per Individual and Condition
8
Nucleic Acid
Bodily Origin
Depositor & Contact
Depositor Characteristics
heavy shedder
Criteria for Shedder Status
determined as in Kanokwongnuwut et al., FSI. Gen 2018, Shedding light on shedders
Previous Activities
wash hands with water, dry with paper towel, wait 15 min before depositing
Contact Scenario
firmly press thumb or fingers for 15 s on surface
Primary Substrate
Primary Substrate Type
metal surfaces (brass, nickel, copper, stainless steel, zinc and aluminium)
Primary Substrate Material
Deposit
firmly press thumb or fingers for 15 s on surface
Delay
0.5 hours to up to 4 weeks time
Secondary Substrate
Secondary Substrate Type
N/A
Secondary Substrate Material
N/A
Secondary Substrate Contact
N/A
Further Transfer
N/A
Sampling
Background DNA on Sampled Surface
Sampling Time
delayed
Persistence
0.5 hours to up to 4 weeks time, stored in airtight clean containers
Sampling Method
swabbing with moistened FLOQSwab
Sampling Area
5 cm2
Laboratory Analysis
Extraction
QIAamp DNA Investigator System™
DNA Quantification
Investigator® Quantiplex Pro RGQ Kit™
Input for Profiling
Either 500 pg of DNA was added to the PCR or 10 µL if the DNA concentration was below 0.05 ng/µL.
Profiling
AmpFLSTR Identifiler™ Plus PCR Amplification Kit 25µL final volume, ProFlex Thermal Cycler, 3500 Genetic Analyzer™
Reference Samples
taken from sole participant
Profile Interpretation and Mixture Analysis
GeneMapper® ID-X (version 1.4), STRmix™ v2.9.0
RNA Data Interpretation
n.a.
Results
DNA Quantity
0.5h/4 weeks average, glass: 0.0213/0.0328 ng/μL, aluminium: 0.0025/0.0092ng/µL, brass: 0.0013/0.0028ng/µL, copper: 0.0050/0.0009ng/µL, nickel: 0.0167/0.0057ng/µL, stainless steel: 0.0024/0.0127ng/µL, zinc: 0.0122/0.0028ng/µL
Profile Quality
0.5 h/4 weeks, glass informative/comparable
Parameter Used for Comparison
DNA quantity, DNA profile quality, likelyhood ratio values
Summary of Results
aluminium: poor initial DNA yields, notable consistent cell loss, no full profiles, but consistent evidenitiary strength and LRs gave extremly strong support, no significant interaction stainless steel: poor initial DNA yields, minimal loss of cells, partial profile at early time points, full profiles at 4 weeks time, all LRs provided extremely strong support for donor inclusion, no siginifcant effect on DNA quality nickel: minimal cell loss, highest initial DNA yield (0.0167 ng/μL), expected decrease over time, mixed profile quality, LRs provided extremely strong support for donor inclusion, no siginifcant effect on DNA quality zinc: notable cell loss, higher initial DNA yields, 0.0122 ng/μL, expected decrease over time, full or nearly full profiles, provided extremely strong support for the inclusion of the donor, weak to no effect copper: irregular cell loss patterns, low DNA yields at both timepoints, No full DNA profiles 24/7 alleles, very strong support of inclusion of the donor, interactions occuring, but not consistent over time brass: cell loss pattern similar to copper, lowest average DNA yield, worse profiles, high degradation, lowest sub-source LRs, extremely strong support for inclusion of the donor, strong immediate effect copper-containing substrates demonstrate moderate short-term persistence, but that the potential to recover sufficient DNA to produce a probative profile diminishes over time on substrates with greater copper content.
Raised Questions
N/A
Cautionary Remarks
limited number of replicates means that natural variation in touch deposits cannot be ruled out as a contributing factor to the observed degradation patterns.