Date of Award

1-1-2021

Language

English

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College/School/Department

Department of Chemistry

Content Description

1 online resource (vii, 33 pages) : illustrations (some color)

Dissertation/Thesis Chair

Igor K Lednev

Committee Members

Paul J Toscano

Keywords

Blood aging, Bloodstain, Chemometrics, Environmental effect, Forensic Science, Raman Spectroscopy, Forensic hematology, Bloodstains, Raman spectroscopy, Chemistry, Forensic, DNA

Subject Categories

Chemistry

Abstract

The development of novel forensic methods is a rapidly growing area within analytical chemistry. Analytical chemistry is well suited for forensic analyses as a plethora of information can be ascertained from utilizing a wide variety of techniques. At the scene of violent crimes, bloodstain evidence is one of the most frequently found and valuable types of evidence. This is because blood is a complex biological fluid which can provide crucial information during a forensic investigation including DNA evidence. The most informative form of analysis is DNA profiling, which potentially allows for the identification of an individual. However, there is more information that can be obtained from additional bloodstain analyses. Time since deposition (TSD) determinations can allow for investigators to draw conclusions as to when a crime occurred. Furthermore, by knowing when the stain was deposited, TSD can give context as to whether a bloodstain is forensically relevant or not, thus ensuring the collection of only pertinent evidence. This results in a streamlined evidence analysis and efficient use of investigator’s time and resources. In this proof-of-concept study Raman spectroscopy paired with chemometrics were utilized for the prediction of TSD for bloodstains aged under an extreme thermal environment (55°C) up to 48 hours post deposition. This temperature was chosen to represent an internal condition of a vehicle left in direct sunlight. Vehicular crime scenes are common and as such it is necessary to investigate how these elevated temperatures can affect bloodstain evidence. It was found that peripheral bloodstains degraded at a faster rate when exposed to an extreme thermal environment than when aged under ambient conditions. Specifically, the first hours’ aging in a heated environment was equivalent to the degradation exhibited after one month of bloodstain aging at room temperature. TSD quantitative predictions were accomplished through the creation of three classification models, a binary and two hourly models. The binary model, used for the differentiation of fresh stains (<24 hours) from older stains (≥24 hours), achieved 97% correct classification for the external validation. The hourly model classed based on the specific hour post deposition, achieved 100% correct classification for the external validation, after application of a manual threshold for individual time points.

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