Forensic Light Sources for the Detection of Body Fluids PDF

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Summary

Notes pertaining to forensic light sources and their use during the forensic analysis of said fluids....

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Forensic Light Sources for the Detection of Body Fluids How Biological Evidence is Detected by ALS  Due to the absorbance of light (blood)  Fluorescent effect (semen, saliva, urine)  The substrate that the fluid is on will effect the absorbance or fluorescence of a liquid Intro  

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DNA can be elicited from biological stains and the sequence of events too BPA FLS—forensic light sources o Laser and high intensity filtered lamps o Make the evidence fluoresce or improves the contrast against the background o Fluorescence—occurs when the light is absorbed and remitted at a lower (longer) wave length  Semen, saliva, and urine  Allows for better contrast for photographic purposes ALS—a non-laser FLS maximum detectable dilution of biological stains by FLS was relatively lower compared to chemical based method

Response of Biological Evidences Towards FLS  Blood o Appear as a dark spot under FLS as it absorbs light (does NOT fluoresce). o Use FLS to enhance the contrast against the background o Highest absorption band occurred between 395nm-435nm with the maximum absorption being at 415nm due to the presence of hemoglobin o Detectable by  IR—reveal stains on black fabric  UV  High intensity LED  Lumatec Superlite  Poliray  Polilight—reveal stains covered by paint  Semen o Very strong photoluminescence substance  Absorbs wavelengths of light (excitation spectrum) an re-emit that light at a longer wave length (emission spectrum)  Emission spec—300-700nm  Excitation spectrum—300-480nm  Need a barrier filer/googles to visualize  Only allow the emission WV through o Best WV for semen detection—420nm and 450nm through orange goggles o Appear yellow-green when subjected to a continuous green beam at 532nm  Observed through an orange laser safety goggles that block 532nm wv o UV light—no goggles needed—blue color o Violet light—Yellow goggles—Yellow

Blue light—Yellow Goggles—Yellow Green—orange goggles—orange Green/yellow light—red goggles—red Green/Yellow—Violet filters (425nm)—black Woods lamp—320-400nm did not work Blue maxx BM500 390-500nm  Detectable even after a few months o Poliray 550nm camera filter was successful Saliva o Fluorescent effect but lower in intensity than semen o Appear blue under UV light o Detectable under exition wavelengths of 266nm and emission of long UV  450nm with orange filter  555nm interference filters  Optimum on white background is 470nm with a 555nm interference filter Long UV [1,9,16] No goggles needed, but recommended to wear UV safety goggles White-bluish 415nm [4,15] Yellow goggles/555nm interference filters Not stated in literature 450nm [4,15] Orange goggles/555nm interference filters White (Orange goggles) 470nm [15] 530nm/555nm interference filters Not stated in literature 490nm [15] 555nm interference filters Not stated in literature 505nm [15] 555nm interference filters Not stated in literature 532nm [9] Goggles that block 532nm light Yellow-orange Weak fluorescence under Polilight o o o o o o

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Urine  May be utilized with UV light but will vary due to the presence of abnormal substances such as glycosuria  Detectable with 415nm, yellow goggles o 450nm orange goggles o 505nm red goggles o 532nm with 532nm filter appeared yellow-ornage but more intense than saliva  No goggles needed, but recommended to wear UV safety  goggles  Depends on abnormal substance presence  415nm, Yellow goggles Not stated in literature  450nm, Orange goggles White  505nm, Red goggles Not stated in literature  532nm, Goggles that block 532nm light Yellow-orange  Exposed by Poliray Star V LEDs Detection of Biological Evidence Using Different FLS  need high intensity light especially for urine  Polilight most tested o Variety of wavelengths

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o Positive results on blood, urine, saliva, semen TracER and Spectra Physics Reveal have narrower bandwidth and higher intensity which makes for better detection Fluorescence of urine was stronger with the laser system o Blood could not be enhanced with the laser due to its absorption Use of LED 370-480nm for the detection of semen, blood, saliva, and urine on skin o Semen and blood detectable by all FLS need less than 3cm application with filter goggles within 20cm o Saliva didn’t fluoresce

Table of FLS and what they Work on

Effect of Biological Evidence on Different Surfaces Towards Their Detection Using FLS  Absorbent fluorescent surfaces allow for the liquid to absorb in and mask the fluorescence of the liquid within.  Blood o Poor on absorbent fleece o Polilight with 415nm on white cotton 1/400 o Blood on skin detectable with high intensity LED and Poliray  Same day 

Semen ser  Best detected at 450nm with orange goggles  May be detected with natural light on most surfaces  Color and the pattern of the clothing affected the appearance of the semen stain o Pink nylon, red and pink cotton, white polka dot and checkered fabrics o White cotton, Pink satin pink fleecy material reduced the fluorescent contrast o 450nm good results on white cotton with barrier filter in place  Fluorescence viewed with high intensity LEDs between 375nm and 480nm with barrier filters on skin o Faint on the second day Saliva  Weak fluorescent capabilities  Absorbency of materials negatively impacted the detection  Sensitive to UV 254nm on Human Skin Mineralight, Evident Products CE 365nm Urine  Only high LED report urine stains with sme lasers being able to detect the presence of urine in human skin Discussion  Best WV is 450nm with orange filter to detect most biological stains (on white cotton all mostly visible)  Limitations o May be human error in detecting the stains with the naked eye thorugh filters and what color they really are o Some fabric would fluoresce or cause issues with the contrast o white cotton would fluorescence at emission wavelength of 440-470nm with 340410nm excitation wavelength and pink satin would fluorescence at emission wavelength of 570-620nm with 490-530nm excitation wavelength  need to vary the WV ad goggles via the fabric in question Future developments  Multispectral imaging system o Processed Captured images in different WV to enhance the background contrast o Automated imaging system would aid in the detection of the biological samples  More precise o...