PMID- 11056272
OWN - NLM
STAT- MEDLINE
DCOM- 20001222
LR  - 20190831
IS  - 0379-0738 (Print)
IS  - 0379-0738 (Linking)
VI  - 115
IP  - 1-2
DP  - 2001 Jan 1
TI  - Vacuum metal deposition: factors affecting normal and reverse development of 
      latent fingerprints on polyethylene substrates.
PG  - 73-88
AB  - Vacuum metal deposition (VMD) is an established technique for the development of 
      latent fingerprints on non-porous surfaces. VMD has advantages over cyanoacrylate 
      fuming, especially in circumstances where prints are old, have been exposed to 
      adverse environmental conditions, or are present on semi-porous surfaces. Under 
      normal circumstances, VMD produces 'negative' prints as zinc deposits onto the 
      background substrate and not the print ridges themselves. A phenomenon of 
      'reverse' development, when zinc deposits onto the print ridges and not the 
      background, has been reported by many authors but its causes have not been 
      conclusively identified. Four plastic substrates were used in this study and 
      these could be easily divided into two groups based on the types of development 
      observed as the amount of deposited gold was increased. On group I plastics, 
      identified as low-density polyethylene (LDPE), normal development then reverse 
      development and finally no development resulted with increasing gold. On group II 
      plastics, identified as high-density polyethylene (HDPE), normal development then 
      over-development and finally poor-quality normal development resulted with 
      increasing gold. Our results suggest that the difference between these plastic 
      types causes variations in the gold film structure which in turn dictates the 
      nature of the zinc deposition. On group I plastics, the structure and thickness 
      of the gold film has been identified as the critical factor in the occurrence of 
      normal or reverse development. Thin gold films on plastic substrates form small 
      'clusters' (or agglomerates) rather than the atoms being uniformly spread over 
      the surface. The size and shape of these clusters is critical. Once the clusters 
      reach a certain morphology, they no longer act as nucleation sites for zinc, and 
      hence, zinc will not deposit onto the substrate. On group II plastics, results 
      suggest that the gold clusters are smaller and more densely packed. Hence, even 
      though the same amount of gold has been deposited, the gold clusters in this case 
      do not reach the critical morphology and so continue to act as nucleation sites 
      for zinc.Typically, zinc will not deposit onto the fingerprint ridges as the gold 
      nucleation sites are buried within the print residue. However, when more gold is 
      deposited, gold emerges at the surface of the latent print allowing zinc 
      deposition onto the ridges. The rate of gold evaporation was found not to affect 
      the structure of the gold film, although a slower rate of evaporation resulted in 
      more effective deposition.
FAU - Jones, N
AU  - Jones N
AD  - Department of Chemistry, Materials and Forensic Science, University of 
      Technology, Sydney, P.O. Box 123, Broadway NSW 2007, Australia.
FAU - Stoilovic, M
AU  - Stoilovic M
FAU - Lennard, C
AU  - Lennard C
FAU - Roux, C
AU  - Roux C
LA  - eng
PT  - Journal Article
PL  - Ireland
TA  - Forensic Sci Int
JT  - Forensic science international
JID - 7902034
RN  - 7440-57-5 (Gold)
RN  - 9002-88-4 (Polyethylene)
RN  - J41CSQ7QDS (Zinc)
SB  - IM
MH  - *Dermatoglyphics
MH  - Forensic Medicine/*methods
MH  - Gold
MH  - Humans
MH  - Mass Spectrometry
MH  - *Polyethylene
MH  - Porosity
MH  - Spectrometry, X-Ray Emission
MH  - Spectrophotometry, Infrared
MH  - Surface Properties
MH  - *Vacuum
MH  - Zinc
EDAT- 2000/11/01 11:00
MHDA- 2001/02/28 10:01
CRDT- 2000/11/01 11:00
PHST- 2000/11/01 11:00 [pubmed]
PHST- 2001/02/28 10:01 [medline]
PHST- 2000/11/01 11:00 [entrez]
AID - S0379-0738(00)00310-8 [pii]
AID - 10.1016/s0379-0738(00)00310-8 [doi]
PST - ppublish
SO  - Forensic Sci Int. 2001 Jan 1;115(1-2):73-88. doi: 10.1016/s0379-0738(00)00310-8.