When an item is submitted to a crime laboratory, the first step in analysis is to examine the item under white light. The next step in examination often involves the use of alternate light sources (ALS) to search for potential biological evidence. Dark adaptation has been suggested as a method to maximize benefits from fluorescent evidence examinations. Dark adaptation refers to the ways the human eye adapts to low light conditions through pupil dilation and rod cell activation. This study evaluates the Crime-lite Eye®, a device designed to help forensic scientists determine their level of dark adaptation before commencing an ALS examination. When tested, the use of the Crime-lite Eye® device resulted in 14% more visualization of fluorescence and 11% more accuracy in pattern recognition, though results were not statistically significant. Since results were more accurate overall, however, and because allowing for a period of dark adaptation would not significantly delay investigation efforts, laboratories should consider implementing a dark adaptation period into their workflow during fluorescent examinations.
Additionally, some ALS manufacturers have begun to include a strobing feature in their devices, such as the GlowTorch FN Forensic Light™. It is known from studies on human attention that flickering stimuli are very effective at capturing attention. Any material fluorescing in response to a strobing ALS would look to the examiner to be suddenly appearing and disappearing as a series of sudden onset stimuli, potentially making weak fluorescence easier to see. Participants in this study were asked to examine four plaid shirts in ambient light conditions and dark conditions, while using either a solid ALS or a strobing ALS. Participants were slightly more accurate while using the strobing ALS device (90% vs 82% in ambient light conditions and 93% vs 92% in dark lighting conditions). However, many of them reported feeling eye strain and annoyance while using the strobing feature. As the change in accuracy was not statistically significant, there is no evidence at present that suggests forensic laboratories need to implement a strobing ALS device into their protocols.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/47977 |
| Date | 30 January 2024 |
| Creators | Miller, Yolonda B. |
| Contributors | Brodeur, Amy N. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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