Pores

Due to the differences in deposition pressure, matrix and substrate conditions, and the minuteness of pores, empirical data shows that intrinsic shapes for pairs of corresponding pores in two impressions from the same source do not reliably record.  As a result, pairs of corresponding pores in two impressions that fail to agree in shape and position are not subject to reduction and are thereby considered neutral.  However, pores between two impressions found to agree in shape and position in which the agreement speaks for itself and allows for demonstration, even to the layman, is assigned a quantitative weight of 5.  The match probability for the single pore feature is subsequently defined as 1/5.

Due to the minuteness of pore structure and ridge unit width and edge contour detail, it is recommended that in the event the comparison of pores and continuous ridge unit shapes and positions between two impressions are required in order to effect individualization, that examination is performed under 25x magnification.

The Continuous Ridge Unit (Ridge Width and Edge Contour)

Similar to pores, due to the differences in deposition pressure, matrix and substrate conditions, empirical data shows that intrinsic shapes for pairs of corresponding ridge units, i.e. ridge widths and edge contours, in two impressions from the same source do not reliably record.  As a result, pairs of corresponding continuous ridge units in two impressions that fail to agree in shape are not subject to reduction and are thereby considered neutral.  However, continuous ridge units between two impressions found to agree in shape in which the agreement speaks for itself and allow for demonstration, even to the layman, is assigned a quantitative weight of 1.15.  The match probability for the continuous ridge unit is subsequently defined as 1/1.15.

Similar to the examination of pore structure, in the event the comparison of continuous ridge unit widths and edge contours between two impressions is required in order to effect individualization, a 25x magnifier is recommended.

Although 25x magnification is adequate to analyze, compare and evaluate pores and ridge edge contours in two impressions, higher magnifications are recommended for purposes of courtroom demonstration.    Pore and ridge edge contour shapes and positions captured under 50x magnification make excellent courtroom exhibits (Figure 1).

Figure 1

Pore and ridge edge contour formations illustrated in "Poroscopy: A Method of Personal Identification Revisited" were captured under 50x magnification [69].   

NEXT PAGE >>>