Gunshot Residue

Where can you collect gunshot residue from?

Hands, hair, face, large objects, clothing

What are the “characteristics” of GSR?

Pb/Ba/Sb (Lead, Barium, Antimony)

What is “consistent” with GSR?

Sb/Ba, Pb/Sb, Pb/Ba

How does CFS GSR analysis work?

Using scanning electron microscopy and energy dispersive spectroscopy only analyzes the inorganic components

What is the hierarchy of propositions for GSR evidence?

• Offence level (III)

• Activity level (II)

• Source level (I)

What is the offence level (III)?

Did the POI shoot the victim?

What is the activity level (II)?

Did the POI discharge a firearm (including or excluding the proviso with the reference combination of firearm ammunition)?

What is source level (I)?

Is the trace arising from the POI hands GSR?

What are environmental sources of GSR-like particles?

• Brake pads

• Fireworks

• Nail guns

• Matches

• Exploded airbags

What were the findings when the cuffs of 100 garments were examined for background levels of GSR?

• 2% of garments had Pb/Sb/Ba particles

• 50% of garments did not have any particles

• The probability of finding one 3-component particle on clothing by chance is 0.01

What is primary transfer?

Occurs during or immediately after a firearm discharge

The initial discharge of a firearm results in what?

The direct deposition of GSR particles onto surfaces in near proximity

What is secondary transfer?

The transfer of GSR to another surface

Contact with surfaces/individuals contaminated with GSR particles during primary transfer may result in what?

Subsequent cross-transfer to a surface that was not present during the initial discharge

What were the findings when firearm-carrying police officers were randomly sampled for GSR?

• ~10% of the officers had at least one characteristic particle present

• Less than 25% probability of transfer particle when simulated arrest situations were used

How many GSR particles are typically found?

0 to 3000

How do shotguns influence GSR deposition and distribution?

• Less characteristic GSR particles in the vicinity of the shooter, especially on the shooting hand

• High levels of contamination to be seen on the supporting hand close to the barrel and in the crook of the supporting arm

How do automatic rifles influence GSR deposition and distribution?

• Both hands are likely to be contaminated due to proximity to the ejection port and muzzle

• Less particle numbers expected than with revolvers and pistols

How time-sensitive is the GSR sample collection?

• 6h, 8h, or 12h depending on the agency is the appropriate time to collect

• Beyond 12h, GSR is not collected

What is the GSR persistence like?

• Rapid loss of GSR in the first few hours after the transfer

• As time after the shooting increases, the number of particles detected decrease

What is the influence of fabric on the collection efficiency of gunshot residue?

• Leather has the greatest persistence due to low shedding

• Cotton was the next persistence

• Wool/viscose/acrylic had the lowest persistence

What is the correlation between shooting distances and total amount of GSR particles?

As shooting distance increases, the amount of GSR particles decrease

What is the frequency of occurrence of chemical classes of the front upper part of upper clothing from the shooting person?

Greatest to least Sb (Sn), Pb, PbSb, PbSbBa/Ba, SbBa

What is the frequency of occurrence of chemical classes of the sleeves from the shooting person?

Greatest to least Pb, Sb (Sn), PbSb, PbSbBa, Pb/Ba, SbBa

What is the frequency of occurrence of chemical classes of the hands from the shooting person?

Greatest to least Sb (Sn), PbSb, PbSbBa, Pb, SbBa, Ba, PbBa

R. v. Glasgow, 2022

• Dr. Hearn said that in his opinion particles identified as gunshot residue originated from a firearm

• “Significant amount of GSR was found on the sample stubs”

• The amount of GSR found would give the conclusion that the vehicle interior was in proximity to the discharge of a firearm, or was exposed to a source of GSR by contact transfer

R. v. Woodcock et al., 2003 - Background

• The presence of GSR indicates that a person who discharged a firearm was close to or came into contact with a surface that had GSR on it

• The number of particles found on a person was not determinative as to whether the person was nearby or fired it

R. v. Woodcock et al., 2003 - Stats

• GSR is lost with time and activity

• About ½ of the GSR on someone is estimated to be lost every 30mins to 60mins

• GSR can go forward, sideways, and upwards of 60ft, and if wind, backwards 30ft

R. v. Woodcock et al., 2003 - Conclusion

GSR can be readily transferred between 2 objects

R. v. Admasu, 2021

• 8 sampling stubs of Mr. Admasu and Mr. Wawryk were submitted

• Dr Hearns testified that one particle characteristic was found on Mr. A's right hand and two on his left and no GSR was found on Mr. W

R. v. Amankwa and Nyadu, 2017 - Background

• Two men were seen running from the area of the shooting (Mr. Amankwa and Nyadu)

• GSR and other evidence was collected ~2 hours after dispatch

R. v. Amankwa and Nyadu, 2017 - GSR

• GSR tests were administered to each hand

  • Web of hand

  • Back of hand

• 3 GSR particles were found on Nyadu

• 0 GSR were found on Amankwa

R. v. Amankwa and Nyadu, 2017 - Conclusion

• Dr. Gerard states that there are possible reasons for the GSR particles found on the hand

  • The person may have recently discharged a firearm

  • The person may have been nearby when a firearm was discharged

  • The person may have had the particles transferred to their hands from contact with another contaminated surface

• Dr. Gerard could not indicate whether any one of the possibilities was more likely than the others

What is OGSR?

Organic gunshot residue

Why OGSR?

• Primer formula that is lead/heavy-metal free

• Designed in 1982 to minimize airborne heavy metals such as Pb, Ba, and Sb to avoid health and environmental issues

What does OGSR discharge?

• DPA

• 4-NDPA

• PbSbBa >100 particles

What is the relation between OGSR particles and time?

• As time increases OGSR decreases

• After 2h 80% of OGSR is lost