From interpreting the incident to pinpointing the perpetrator, the presence of blood at a crime scene can provide clues vital to solving a crime. Since the advent of DNA profiling in the 1980s, police have been able to use DNA to link suspects to crime scenes, making the detection and collection of biological evidence more important than ever before. However successful DNA profiling relies on a positive match with either a DNA profile from a suspect or one stored in a database. With nothing to compare a profile to, the DNA is of limited use and the trail may quickly run cold.
But what if investigators could gain even more information from a bloodstain at a crime scene? What if it were possible to rapidly figure out whether the donor was male or female, or establish their race? And all of this without shipping samples back to the lab.
New research conducted at the University at Albany in New York has demonstrated that it may be possible to establish some individual donor characteristics in a matter of minutes.
Past research has already demonstrated that the biochemical composition of blood differs between males and females and individuals of different races. But the ability to obtain this information on-site at the crime scene in a matter of minutes could change the way body fluids are processed. In a recent study, Prof. Igor Lednev and his team applied a technique known as attenuated total reflection Fourier transform-infrared (ATR FTIR) spectroscopy to blood analysis, with the aim of establishing whether characteristics such as sex and race can be determined from bloodstains.
FTIR is an analytical technique capable of providing information about a material’s chemical information. In brief, the device directs infrared radiation towards the sample. Some of this radiation is absorbed by the material, and some passes through. The sample’s absorbance of this light at different wavelengths is measured and used to determine the material’s chemical information. After analysis a spectrum is produced, which acts as a kind of molecular ‘fingerprint’ of the sample. The different features in the spectrum relate to the different chemical components in the sample.
Infrared spectra were produced by analysing the blood of 30 donors (a mixture of male and females of Caucasian, African American and Hispanic racial origin). From this, researchers could observe any differences occurring between blood from male and females, and blood from members of different races. Using this data, the researchers built a model capable of classifying samples based on their chemical profile. By taking the chemical profile of an unknown bloodstain and comparing it with a model containing bloodstains from numerous different groups, the model can predict the likely classification (i.e. whether the donor was male or female and which racial group they belong to). In this study, it correctly classified bloodstains around 90% of the time.
Using infrared-based techniques has a number of advantages over other methods of analysis. As the technique simply necessitates the direction of light towards the bloodstain, the technique is non-destructive. Inevitably this is perfect for criminal investigations – destroying the evidence is never ideal. IR spectroscopy is also amenable to portability, lending itself well to on-the-go analysis at crime scenes and so potentially saving a lot of time by avoiding sending unnecessary samples back to the lab for analysis.
Although only a pilot study, this research has demonstrated the possibility of establishing donor characteristics through the rapid and non-destructive analysis of bloodstains. The ability to determine features such as sex and race would enable police to significantly narrow down the search for suspects or victims, ultimately preserving valuable time and money. Furthermore, the ability of FTIR to non-destructively analyse evidence on-site renders it an ideal tool for forensic analysis. Inevitably a great deal more research will be necessary, and if the technique ever becomes operational, it would be years before such technology and methods were suitable for deployment to crime scenes and use as evidence in criminal trials.
Mistek et al. Phenotype profiling for forensic purposes: nondestructive potentially on scene attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy of bloodstains. Forensic Chemistry. 2019, In Press.
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