Specific fluorescent signatures for body fluid identification using fluorescence spectroscopy

Abstract

Non-invasive, rapid, on-site detection and identification of body fluids is highly desired in forensic investigations. The use of fluorescence-based methods for body fluid identification, have so far remain relatively unexplored. As such, the fluorescent properties of semen, serum, urine, saliva and fingermarks over time were investigated, by means of fluorescence spectroscopy, to identify specific fluorescent signatures for body fluid identification. The samples were excited at 81 different excitation wavelengths ranging from 200 to 600 nm and for each excitation wavelength the emission was recorded between 220 and 700 nm. Subsequently, the total emitted fluorescence intensities of specific fluorescent signatures in the UV–visible range were summed and principal component analysis was performed to cluster the body fluids. Three combinations of four principal components allowed specific clustering of the body fluids, except for fingermarks. Blind testing showed that 71.4% of the unknown samples could be correctly identified. This pilot study shows that the fluorescent behavior of ageing body fluids can be used as a new non-invasive tool for body fluid identification, which can improve the current guidelines for the detection of body fluids in forensic practice and provide the robustness of methods that rely on fluorescence.

Analysis of the fluorescent properties of vaginal fluid upon ageing

“…Multiple similarities were found between the fluorescent characteristics of vaginal fluid samples and other forensic relevant biological samples [3,8,11,19].…”

“…The first fluorescence peak that could be observed in both vaginal fluid stains and other biological samples such as semen, saliva, fingermarks, serum and menstrual blood, has an emission peak at 300-350 nm upon excitation at 220-230 nm [11]. This fluorescence peak is formed in proteins containing aromatic amino acids, i.e.…”

“…However, the ability to detect stains with this method is limited by the fact that fluorescence intensity and the optimal excitation and emission wavelengths can change when samples dry or upon ageing. Other limiting factors include the lowintensity fluorescence of some body fluids and the fact that some fluorescentor highly absorbing substrates can reduce or mask the stains' fluorescence [10,11]. Additionally, ALS can only be used as an indicative test, but cannot be used to identify which body fluid is present [12].…”

Stand‐off Raman spectroscopy is a promising approach for the detection and identification of bloodstains for forensic purposes

“…8 Fluorescence spectroscopy is another promising nondestructive method utilized for the detection of all main body fluids. 9 Raman spectroscopy has great potential as a universal tool for the confirmatory and nondestructive identification of body fluid traces. 10 In this technique, inelastically scattered light is collected while irradiating a sample with monochromatic light.…”

“…The nondestructive nature of FTIR‐ATR makes it advantageous for forensic trace evidence analysis 8 . Fluorescence spectroscopy is another promising nondestructive method utilized for the detection of all main body fluids 9 . Raman spectroscopy has great potential as a universal tool for the confirmatory and nondestructive identification of body fluid traces 10 .…”