Forensics Journal - Stevenson University 2011 | Page 57

FORENSICS JOURNAL

processed with non-magnetic powder and magnetic powders were
captured with white or natural light. The upconversion processed substrates were captured with a Schott GG495 476 nm yellow filter and
the infrared laser as well as additional white light. All substrates were
placed on top of a black semi-glossy backing paper to minimize any
additional background fluorescence. When a fingerprint was captured
on one half of the substrate, the same fingerprint on the other half of
the substrate was also photographed. The two were visually compared
and aligned side-by-side using a photo editing program at a later
time.

FIGURE 1: These were the steps taken to powder the two halves of
the substrate and perform a side-by-side comparison for a depletion
series. The green [right] side represents the upconversion powder and
the purple [left] side is the fingerprint powder being compared to the
upconversion powder.

Scanning Electron Microscope (SEM)

Step 1

Step 2

Step 3

The Scanning Electron Microscope (SEM) was utilized to examine
the entire spectrum of fingerprint powders used in this research. The
instrument was a Hitachi Science Systems, Ltd. Scanning Electron
Microscope S-3500N (mfg #1226-07) with an EDAX detecting unit
model 3500N with an active area of 10mm2 (serial #8273-46210).
Each powder (non-magnetic, magnetic, fluorescent, and upconversion) was obtained for adhesion to aluminum mounting stubs (cat
#75220) with carbon adhesive tabs (cat #77825-12) acquired from
Electron Microscopy Sciences. The Hitachi PC SEM program was
opened on the computer and the vacuum system was turned off
before inserting a sample. Once the vacuum was completely evacuated, the stub holding the powder was placed onto the stub holder
and screwed tightly in place. The chamber under the vacuum was
sealed again and the high voltage was initiated. The sample was
scanned in TV mode so that the image is produced instantaneously
in order to begin to focus the image. Images were captured in High
Resolution mode to be saved to the computer. The images produced
were later used to determine particle size and shape. Particle size was
measured with the Quartz PCI-Image Management system and calibrated according to magnification using the micron marker.

Step 4

After the deposition of the fingerprints, the substrate was cut in half
or through the center of the prints in order to obtain a side-by-side
comparison between the two treatments used. This can be a disadvantage since there is less of the fingerprint to evaluate, but it aids the
researcher by allowing her Ѽ