Estimation of the age of human bloodstains by electron paramagnetic resonance spectroscopy: long-term controlled experiment on the effects of environmental factors

Alkaline Phosphatase for Estimating the Time since Deposition of Blood Fingerprints by Scanning Electrochemical Microscopy

Blood is one of the most frequent and valuable traces encountered at crime scenes, where knowing the time since deposition (TSD) of bloodstains tremendously assists forensic experts to screen out crime-related evidence and aids in the reconstruction of the event sequence. Although increasing proof-of-concept methodologies for investigating the TSD of bloodstains have been reported, there is still no accepted strategy in forensic practice as the aging mechanism involves complex components, leading to the inaccuracy of the estimation results. Herein, an endogenous biomarker of alkaline phosphatase (ALP) was chosen to investigate the TSD by scanning electrochemical microscopy (SECM). Results demonstrate that the ALP activity acquired via SECM lateral scan assay exhibited a clear decrease over time, and a similar trend was observed on both poly(vinylidene fluoride) (PVDF) membrane and glass, with the aging kinetics on PVDF membrane being faster than glass. By means of quantitatively calculating the flux of generated p-aminophenol (PAP), we established the aging curve and realized the TSD estimation of blood fingerprints (BFPs) that was unable to be distinguished via optical measurements. Intriguingly, the as-obtained estimation accuracy ranged from 74.6 to 93.7%, proving the possibility of using an ALP biomarker and SECM. More appealingly, the predicted TSDs were capable of accurately differentiating the deposition sequence of overlapping BFPs, which was hardly achieved by optical means. Therefore, this proof-of-concept strategy demonstrates the value of SECM as a forensic tool and opens possibilities for revealing multidimensional information about crime.

Forensic analysis of biological fluid stains on substrates by spectroscopic approaches and chemometrics: A review

BACKGROUND

Bodily fluid stains are one of the most relevant evidence that can be found at the crime scene as it provides a wealth of information to the investigators. They help to report on the individuals involved in the crime, to check alibis, or to determine the type of crime that has been committed. They appear as stains in different types of substrates, some of them porous, which can interfere in the analysis. The spectroscopy techniques combined with chemometrics are showing increasing potential for their use in the analysis of such samples due to them being fast, sensitive, and non-destructive.

FINDINGS

This is a comprehensive review of the studies that used different spectroscopic techniques followed by chemometrics for analysing biological fluid stains on several surfaces, and under various conditions. It focuses on the bodily fluid stains and the most suitable spectroscopic techniques to study forensic scientific problems such as the substrate's characteristics, the influence of ambient conditions, the aging process of the bodily fluids, the presence of animal bodily fluids and non-biological fluids (interfering substances), and the bodily fluid mixtures. The most widely used techniques were Raman spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR). Nonetheless, other non-destructive techniques have been also used, like near infrared hyperspectral imaging (HSI-NIR) or surface enhanced Raman spectroscopy (SERS), among others. This work provides the criteria for the selection of the most promising non-destructive techniques for the effective in situ detection of biological fluid stains at crime scene investigations.

SIGNIFICANCE AND NOVELTY

The use of the proper spectroscopic and chemometric approaches on the crime scene is expected to improve the support of forensic sciences to criminal investigations. Evidence may be analysed in a non-destructive manner and kept intact for further analysis. They will also speed up forensic investigations by allowing the selection of relevant samples from occupational ones.

Age estimation of bloodstains based on Raman spectroscopy and chemometrics

The accurate estimation of the bloodstain age, which is one of the important biological evidence of crime scene, can provide a lot of information related to crime. How to extract the information quickly and accurately from bloodstains without damage has been a focused problem. In this study, a bloodstains age estimation method based on Raman spectroscopy and chemometrics was developed. As many as 11 simulated environments based on different temperature and humidity were constructed in the method, and bloodstains of three species including human were studied. The influence of environmental factors such as temperature and humidity on the variation of Raman spectral peaks during the aging process of bloodstains was analyzed using the e-index fitting. When the humidity was kept constant, the increase of temperature generally promoted the changes of the spectral peaks. When the temperature was kept constant, the increase of humidity generally slowed the changes of spectral peaks. These works provide data support for the further development of Raman spectroscopy for bloodstain age estimation and could accelerate its application in actual scenes.

Validation of the Metabolite Ergothioneine as a Forensic Marker in Bloodstains

Ergothioneine, which is a naturally occurring metabolite, generally accumulates in tissues and cells subjected to oxidative stress, owing to its structural stability at physiological pH; therefore, it has been attracting attention in various biomedical fields. Ergothioneine has also been suggested as a potential forensic marker, but its applicability has not yet been quantitatively validated. In this study, quantitative analysis of ergothioneine in bloodstains was conducted to estimate the age of bloodstains and that of bloodstain donors. Blood from youth and elderly participants was used to generate bloodstains. After extracting metabolites from the bloodstains under prevalent age conditions, ergothioneine levels were quantified by mass spectrometry via multiple reaction monitoring. The concentration of ergothioneine in day 0 bloodstains (fresh blood), was significantly higher in the elderly group than in the youth group, but it did not differ by sex. Statistically significant differences were observed between the samples from the two age groups on days 0, 5 and 7, and on days 2 and 3 compared with day 0. The findings suggest that ergothioneine can be used to estimate the age of bloodstains and of the donor; it could be useful as a potential marker in reconstructing crime scenes.

Bloodstain Metabolite Markers: Discovery and Validation for Estimating Age of Bloodstain within 7 Days

Metabolomic research using analytical chemistry methods has been carried out in a wide range of research fields. However, research combining forensic science and metabolomics is rare. Determining the age of bloodstains could provide key information regarding when a crime was committed. Currently, validated methods for estimating the age of bloodstains are unavailable. Metabolites are intermediate and final products of chemical reactions. Therefore, they are less likely to be degraded than other components of blood under field conditions. In this study, metabolites in bloodstains were analyzed using liquid chromatography-mass spectrometry to discover and validate metabolic markers for determining the age of bloodstains within a week post-bleeding. Nontargeted analysis of bloodstain metabolites revealed statistically significant differences over time. Quantitative analysis of identified candidates via multiple reaction monitoring confirmed the statistical significance according to the age of bloodstain. Pyroglutamic acid, l-glutamine, acetylcarnitine, and adenosine 5'-monophosphate were selected as the final markers. The content of each marker exhibited a statistically significant and consistent tendency to decrease with the age of bloodstain. Furthermore, the effect of hemolysis was considered according to the blood fraction spots of the four markers. This study is the first to identify and validate metabolite markers that may help determine the age of bloodstains within a week post-bleeding. If applied to crime scenes as indicators of the age of bloodstains, they can be used as innovative and important tools for reconstructing crime scenes, suggesting initial investigative direction. This study highlights the forensic utility of blood metabolites ex vivo.

The estimation of bloodstain age utilizing circRNAs and mRNAs biomarkers

Determining the time since deposition (TsD) of bloodstains can provide forensic investigators with additional clues, as it can corroborate eyewitness accounts, limit the number of suspects, and help confirm alibis. Bloodstains are the most common bodily fluid stains at crime scenes. In this study, we examined the relative expression levels (REs) of circRNAs and mRNAs data in bloodstains over ten time points by Real-time quantitative polymerase chain reaction (qPCR), to determine the utility of the relative expression levels of RNA markers for TsD estimation. Forensic samples more than just appear in indoor settings, we also evaluated the use of RNA degradation rate to indicate the age of bloodstains in different environments including indoor and outdoor conditions. The expression levels of six blood-specific mRNA markers (GYPA, CD93, ALAS2, SPTB, HBB, HBA), three highly expressed circRNAs in human peripheral blood (hsa_circ_0001445, hsa_circ_0000972, hsa_circ_0000095) and three reference genes (18 S, ACTB and U6) were analyzed across numerous ageing time points. Analysis of the degradation rates of individual RNAs under indoor and outdoor conditions showed that they exhibited a unique degradation profile during the four-month storage interval, with both circRNAs and mRNAs linearly showing continuous degradation, while U6 is more stable than other reference gene markers. In the current study, we firstly used circRNAs as additional novel biomarkers for bloodstain age estimation, and at the same time proved that different environments had a significant impact on the REs of certain blood biomarkers, and sex differences did not affect the age estimation of bloodstains. The REs of the selected RNA molecules in this study showed a non-linear relationship with bloodstain age and the mathematical formula for estimating the bloodstain age based on the relative expression levels of hsa_circ_0001445, ALAS2 and HBB can be used to estimate the TsD of bloodstains from the REs of bloodstains of unknown age, which represent a potentially effective approach to looking for time-dependent changes and TsD estimation.

Unlocking the potential of forensic traces: Analytical approaches to generate investigative leads

Forensic investigation involves gathering the information necessary to understand the criminal events as well as linking objects or individuals to an item, location or other individual(s) for investigative purposes. For years techniques such as presumptive chemical tests, DNA profiling or fingermark analysis have been of great value to this process. However, these techniques have their limitations, whether it is a lack of confidence in the results obtained due to cross-reactivity, subjectivity and low sensitivity; or because they are dependent on holding reference samples in a pre-existing database. There is currently a need to devise new ways to gather as much information as possible from a single trace, particularly from biological traces commonly encountered in forensic casework. This review outlines the most recent advancements in the forensic analysis of biological fluids, fingermarks and hair. Special emphasis is placed on analytical methods that can expand the information obtained from the trace beyond what is achieved in the usual practices. Special attention is paid to those methods that accurately determine the nature of the sample, as well as how long it has been at the crime scene, along with individualising information regarding the donor source of the trace.

Analysis of the influence of EDTA-treated reference samples on forensic bloodstain age estimation

The age estimation of blood traces provides important leads for the chronological assessment of criminal events and their reconstruction. To determine bloodstain age, experimental comparative data from a laboratory environment are used. Under these conditions the utilization of anticoagulants such as EDTA helps to suppress the blood clotting mechanism to allow the examination over a longer time period. This unnatural prevention of blood coagulation is highly questionable when estimating bloodstain age, since the blood's physical and chemical properties are altered. For this reason, the authors determined actual influence of EDTA on blood spectra over time in order to formulate a statement as to whether this effect can be measured. Human and porcine blood samples were aged under controlled conditions. The resulting UV/VIS spectra were separated into their individual components using signal separation techniques, allowing the changes in the ratios of the individual hemoglobin derivatives to be observed over time. The results show a significant influence of EDTA on the conversion of oxyhemoglobin to methemoglobin and a minor influence on the conversion of methemoglobin to hemichrome within the relevant time range of 5-100 h. The use of EDTA thus slows down the aging process of blood spots. To illustrate the great influence of EDTA, spectra of untreated pig blood samples were included as comparison data. These show that the difference between EDTA-treated and untreated blood samples is as great as the difference between human blood and pig blood. As a consequence of our findings experimental comparative data for the age estimation of bloodstains should never result from EDTA-treated blood.

Feature Selection and Rapid Characterization of Bloodstains on Different Substrates

Establishing the precise timeline of a crime can be challenging as current analytical techniques used suffer from many limitations and are destructive to the body fluids encountered at crime scenes. Raman spectroscopy has demonstrated excellent potential in forensic science as it provides direct information about the structural and molecular changes without the need for processing or extracting samples. However, its current applicability is limited to pure body fluids, as signals from the substrate underlying these fluids greatly influence the current models used for age estimation. In this study, we utilized Raman spectroscopy to identify selective spectral markers that delineate the bloodstain age in the presence of interfering signals from the substrate. The pure bloodstains and the bloodstains on the substrate were aged for two weeks at 21 ± 2 ℃ in the dark. Least absolute shrinkage and selection operator (LASSO) regression was employed to guide the feature selection in the presence of interference from substrates to accurately predict the bloodstain age. Substrate-specific regression models guided by an automated feature selection algorithm yielded low values of predictive root mean square error (0.207, 0.204, 0.222 h in logarithmic scale) and high R² (0.924, 0.926, 0.913) on test data consisting of blood spectra on floor tile, facial tissue, and linoleum-polymer substrates, respectively. This framework for an automated feature selection algorithm relies entirely on pure bloodstain spectra to train substrate-specific models for estimating the age of composite (blood on substrate) spectra. The model can thus be easily applied to any new composite spectra and is highly scalable to new environments. This study demonstrates that Raman spectroscopy coupled with LASSO could serve as a reliable and nondestructive technique to determine the age of bloodstains on any surface while aiding forensic investigations in real-world scenarios.

Age Determination of Blood-Stained Fingerprints Using Visible Wavelength Reflectance Hyperspectral Imaging

The ability to establish the exact time a crime was committed is one of the fundamental aims of forensic science. The analysis of recovered evidence can provide information to assist in age determination, such as blood, which is one of the most commonly encountered types of biological evidence and the most common fingerprint contaminant. There are currently no accepted methods to establish the age of a blood-stained fingerprint, so progress in this area would be of considerable benefit for forensic investigations. A novel application of visible wavelength reflectance, hyperspectral imaging (HSI), is used for the detection and age determination of blood-stained fingerprints on white ceramic tiles. Both identification and age determination are based on the unique visible absorption spectrum of haemoglobin between 400 and 680 nm and the presence of the Soret peak at 415 nm. In this study, blood-stained fingerprints were aged over 30 days and analysed using HSI. False colour aging scales were produced from a 30-day scale and a 24 h scale, allowing for a clear visual method for age estimations for deposited blood-stained fingerprints. Nine blood-stained fingerprints of varying ages deposited on one white ceramic tile were easily distinguishable using the 30-day false colour scale.

Estimation of the age of human bloodstains under the simulated indoor and outdoor crime scene conditions by ATR-FTIR spectroscopy

Estimation of the age of human bloodstains is of great importance in forensic practices, but it is a challenging task because of the lack of a well-accepted, reliable, and established method. Here, the attenuated total reflection (ATR)-Fourier transform infrared (FTIR) technique combined with advanced chemometric methods was utilized to determine the age of indoor and outdoor bloodstains up to 107 days. The bloodstain storage conditions mimicked crime scene scenarios as closely as possible. Two partial least squares regression models—indoor and outdoor models with 7–85 days—exhibited good performance for external validation, with low values of predictive root mean squared error (5.83 and 4.77) and high R² values (0.94 and 0.96) and residual predictive deviation (4.08 and 5.14), respectively. Two partial least squares–discriminant analysis classification models were built and demonstrated excellent distinction between fresh (age ≤1 d) and older (age >1 d) bloodstains, which is highly valuable for forensic investigations. These findings demonstrate that ATR-FTIR spectroscopy coupled with advanced chemometric methods can be employed as a rapid and non-destructive tool for age estimation of bloodstains in real-world forensic investigation.

Ages at a Crime Scene: Simultaneous Estimation of the Time since Deposition and Age of Its Originator

Blood is a major contributor of evidence in investigations involving violent crimes because of the unique composition of proteins and low molecular weight compounds present in the circulatory system, which often serve as biomarkers in clinical diagnostics. It was recently shown that biomarkers present in blood can also identify characteristics of the originator, such as ethnicity and biological sex. A biocatalytic assay for on-site forensic investigations was developed to simultaneously identify the age range of the blood sample originator and the time since deposition (TSD) of the blood spot. For these two characteristics to be identified, the levels of alkaline phosphatase (ALP), a marker commonly used in clinical diagnostics corresponding to old and young originators, were monitored after deposition for up to 48 h to mimic a crime scene setting. ALP was chosen as the biomarker due to its age-dependent nature. The biocatalytic assay was used to determine the age range of the originator using human serum samples. By means of statistical tools for evaluation and the physiological levels of ALP in healthy people, the applicability of this assay in forensic science was shown for the simultaneous determination of the age of the originator and the TSD of the blood spot. The stability of ALP in serum allows for the differentiation between old and young originators up to 2 days after the sample was left under mimicked crime scene conditions.

A Raman "spectroscopic clock" for bloodstain age determination: the first week after deposition

Knowing the time since deposition (TSD) of an evidentiary bloodstain is highly desired in forensics, yet it can be extremely complicated to accurately determine in practice. Although there have been numerous attempts to solve this problem using a variety of different techniques, currently, no established, well-accepted method exists. Here, a Raman spectroscopic approach was developed for determining the age of bloodstains up to 1 week old. Raman spectroscopy, along with two-dimensional correlation spectroscopy (2D CoS) and statistical modeling, was used to analyze fresh bloodstains at ten time points under ambient conditions. The 2D CoS results indicate a high correlation between several Raman bands and the age of a bloodstain. A regression model was built to provide quantitative predictions of the TSD, with cross-validated root mean squared error and R (2) values of 0.13 and 0.97, respectively. It was determined that a "new" (1 h) bloodstain could be easily distinguished from older bloodstains, which is very important for forensic science in helping to establish the relevant association of multiple bloodstains. Additionally, all bloodstains were confirmatively identified as blood by comparing the experimentally measured spectra to multidimensional body fluid spectroscopic signatures of blood, saliva, semen, sweat, and vaginal fluid. These results demonstrate that Raman spectroscopy can be used as a nondestructive analytical tool for discriminating between bloodstains on the scale of hours to days. This approach shows promise for immediate practical use in the field to predict the TSD with a high degree of accuracy. Graphical Abstract Bloodstain aging over time illustrating naturally ocurring processes.

Forensic determination of blood sample age using a bioaffinity-based assay

A bioaffinity-driven cascade assay was developed to determine the time elapsed from the point a blood sample was left at a crime scene to the point of discovery.

Biphasic oxidation of oxy-hemoglobin in bloodstains

Background

In forensic science, age determination of bloodstains can be crucial in reconstructing crimes. Upon exiting the body, bloodstains transit from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO₂) to met-hemoglobin (met-Hb) and hemichrome (HC). The fractions of HbO₂, met-Hb and HC in a bloodstain can be used for age determination of bloodstains. In this study, we further analyze the conversion of HbO₂ to met-Hb and HC, and determine the effect of temperature and humidity on the conversion rates.

Methodology

The fractions of HbO₂, met-Hb and HC in a bloodstain, as determined by quantitative analysis of optical reflectance spectra (450–800 nm), were measured as function of age, temperature and humidity. Additionally, Optical Coherence Tomography around 1300 nm was used to confirm quantitative spectral analysis approach.

Conclusions

The oxidation rate of HbO₂ in bloodstains is biphasic. At first, the oxidation of HbO₂ is rapid, but slows down after a few hours. These oxidation rates are strongly temperature dependent. However, the oxidation of HbO₂ seems to be independent of humidity, whereas the transition of met-Hb into HC strongly depends on humidity. Knowledge of these decay rates is indispensable for translating laboratory results into forensic practice, and to enable bloodstain age determination on the crime scene.

Estimation of the postmortem duration of mouse tissue by electron spin resonance spectroscopy

Electron spin resonance (ESR) method is a simple method for detecting various free radicals simultaneously and directly. However, ESR spin trap method is unsuited to analyze weak ESR signals in organs because of water-induced dielectric loss (WIDL). To minimize WIDL occurring in biotissues and to improve detection sensitivity to free radicals in tissues, ESR cuvette was modified and used with 5,5-dimethtyl-1-pyrroline N-oxide (DMPO). The tissue samples were mouse brain, hart, lung, liver, kidney, pancreas, muscle, skin, and whole blood, where various ESR spin adduct signals including DMPO-ascorbyl radical (AsA(∗)), DMPO-superoxide anion radical (OOH), and DMPO-hydrogen radical (H) signal were detected. Postmortem changes in DMPO-AsA(∗) and DMPO-OOH were observed in various tissues of mouse. The signal peak of spin adduct was monitored until the 205th day postmortem. DMPO-AsA(∗) in liver (y = 113.8-40.7 log (day), R1 = -0.779, R2 = 0.6, P < .001) was found to linearly decrease with the logarithm of postmortem duration days. Therefore, DMPO-AsA(∗) signal may be suitable for detecting an oxidation stress tracer from tissue in comparison with other spin adduct signal on ESR spin trap method.

EPR Study of Iron Ion Complexes in Human Blood

Electronic states of iron ion complexes in human blood from patients with melanoma have been investigated by electron paramagnetic resonance (EPR). The measurements were performed at liquid nitrogen temperature (77 K) on an X-band EPR spectrometer. Numerous types of iron paramagnetic centers have been identified. In several kinds of protein complexes exemplified by methemoglobin, transferrin or ferritin, various forms of trivalent iron have been found. Three groups of patients with typical EPR spectra have been individualized. These groups differed in types and concentration of paramagnetic centers in peripheral blood. A good correlation has been found between the EPR results, the total iron ion complexes concentration and transferrin saturation.

An RNA expression method for aging forensic hair samples

A common limitation to most forensic trace evidence analysis is the ability to determine the time at which the evidence was deposited at the crime scene. This issue of timing is vitally important as it may not only reveal when the crime occurred, but could exclude potential suspects from the investigation. Using a reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay, we monitored the relative expression ratio (RER) of two different RNA species (18S and β-actin) in hair samples that were aged naturally over a period of 3 months. No gender or age-of-donor biases were observed, and results were linear up to 60 days. After 60 days, the results were more variable and gave unreliable estimates of time since deposition. Overall, the results presented in this paper suggest that the age of hair samples containing follicular tags can be approximated using a second-order polynomial, although with limitations: Age = 3.31RER(2) - 2.85RER - 0.54 (R(2) = 0.98).

Non-contact spectroscopic determination of large blood volume fractions in turbid media

We report on a non-contact method to quantitatively determine blood volume fractions in turbid media by reflectance spectroscopy in the VIS/NIR spectral wavelength range. This method will be used for spectral analysis of tissue with large absorption coefficients and assist in age determination of bruises and bloodstains. First, a phantom set was constructed to determine the effective photon path length as a function of μ(a) and μ(s)' on phantoms with an albedo range: 0.02-0.99. Based on these measurements, an empirical model of the path length was established for phantoms with an albedo > 0.1. Next, this model was validated on whole blood mimicking phantoms, to determine the blood volume fractions ρ = 0.12-0.84 within the phantoms (r = 0.993; error < 10%). Finally, the model was proved applicable on cotton fabric phantoms.

Electron spin resonance. Part one: a diagnostic method in the biomedical sciences

A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the biomedical sciences. Specifically considered are: spin-trapping in biological media; the determination of antioxidant efficiencies; lipid-peroxidation; the use of nitroxides as probes of metabolic activity in cells and as structumral probes of cell-membranes; ESR coupled with materials for radiation-dosimetry; food- and drug-irradiation; studies of enzyme systems and ofcyclodextrins; diagnosis of cancer and rheumatoid arthritis; measurement of oxidative stress in synovial tissue in preparation for joint replacement; determination of oxidative species during kidney dialysis; measurement of biological oxygen concentrations (oximetry); trapping in living cells of the endothelium-derived relaxing factor nitric oxide (NO); measurement of hydrogen peroxide; determination of drugs of abuse (opiates); ESR measurements of whole blood and as a means to determine the age of bloodstains for forensic analysis are surveyed, and also a determination of the aqueous volume of human sperm cells is described, among other topics.

Multivariate analysis for estimating the age of a bloodstain

Our objective is to provide crime laboratories with a technique for estimating the age of a bloodstain. Toward that goal, we have used multiplexed, real-time RT-PCR (or qPCR) to determine the relative stability of different-sized segments of the same RNA species as well as differences in stability between two different RNAs' change over time in bloodstains. Our results indicate that a multivariate analysis of the changing ratio of the different RNA segments can be used to differentiate between samples of different ages in the defined population. Bloodstains from 29 of 30 donors could be partitioned into different ages using this technique. Although further improvements will be required before this approach can be implemented in crime laboratories, the multivariate analysis holds promise of providing a reliable approach for temporally linking a bloodstain to the commission of a crime or excluding a bloodstain as being irrelevant to the case in question.