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Determination of the Time since Deposition (TsD) of biological traces

English title Determination of the Time since Deposition (TsD) of biological traces
Applicant Haas Cordula
Number 175854
Funding scheme Project funding (Div. I-III)
Research institution Institut für Rechtsmedizin Universität Zürich-Irchel
Institution of higher education University of Zurich - ZH
Main discipline Molecular Biology
Start/End 01.07.2018 - 30.06.2021
Approved amount 345'050.00
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All Disciplines (2)

Discipline
Molecular Biology
Genetics

Keywords (6)

proteomics; transcriptomics; body fluids; forensic science; genomics; time since deposition

Lay Summary (German)

Lead
Bei der Aufklärung sowohl von Verbrechen als zunehmend auch von terroristischen Straftaten spielt die forensische DNA-Analyse eine zentrale Rolle. Durch einen Vergleich der individualspezifischen DNA-Profile kann ein Beweisstück zweifelsfrei einer Person zugeordnet werden. Bis anhin ist es aber nicht möglich das Alter einer Spur zu bestimmen, bzw. den Zeitpunkt, an dem die Spur am Tatort zurückgelassen wurde. Somit kann die Spur nicht eindeutig mit der Tat in Verbindung gebracht werden. In diesem Projekt sollen experimentelle Methoden und statistische Verfahren entwickelt werden, um das Alter einer Spur bestimmen zu können.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Biomoleküle sind zeit- und umweltabhängigen Veränderungen unterworfen, welche man für die Bestimmung des Spurenalters nutzen könnte. Diese Veränderungen im Genom (DNA), Transkriptom (RNA) und Proteom (Proteine) sollen an forensischen Spuren mittels Hochdurchsatz-Sequenzierung und Massenspektrometrie systematisch untersucht werden. In diesen Daten wird nach spezifischen Markern gesucht, die sich über die Zeit verändern. Für ausgewählte Marker sollen anschliessend einfache experimentelle Nachweismethoden etabliert werden. Mittels statistischer Verfahren wird ein Vorhersagemodell zur zuverlässigen Bestimmung des Alters von biologischen Spuren entwickelt.

 

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Das Spurenalter ist eine wichtige Information, um die Relevanz einer biologischen Spur im Zusammenhang mit einem Kriminalfall zu beurteilen. Dies wird den ermittelnden Behörden helfen die wahren Täter zu identifizieren und unrechtmässig beschuldigte Personen zu entlasten.

Direct link to Lay Summary Last update: 15.06.2018

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Abstract

In the investigation of crime and recently also terrorist attacks, forensic DNA analysis plays a crucial role in identifying the source of biological evidence. By DNA analysis, experts can link evidence such as bloodstains to a person by comparing DNA profiles which are specific to individuals. However, the potential of nucleic acid analysis to linking evidence not only to a person, but to the crime itself, is hitherto not fully exploited and evaluated. Particularly, the exact time point at which evidence has been deposited at a crime scene is not yet part of scientific trace analysis. But information on the age of a trace, or, more precisely, the time since deposition (TsD) of traces would be crucial for the determination of the relevance of evidence in the investigative process. For example, if the trace has been deposited at the estimated time point of the crime, it has a high relevance while the relevance of older/younger traces is low, because their deposition might not be related to the crime itself.To bridge this gap in current molecular trace analysis, we will:•exploit the time-dependent changes in the molecular structure of RNA, DNA and proteins•use novel massive parallel sequencing and mass spectrometry to obtain global degradation patterns of these molecules•combine respective expertise in forensic RNA, DNA and protein analysis in Münster and Zurich to provide a comprehensive overview of each molecule’s potential as marker •develop marker assays for reliable determination of the time since deposition (TsD) of biological traces•develop a prediction model for TsD determination.To achieve these aims, we will identify suitable areas within the human genome, transcriptome and proteome which show susceptibility to time-dependent structural changes. Work on genome will be performed in Münster, Germany, while work on transcriptome and proteome will be performed in Zurich, Switzerland. Identified markers will be combined in targeted assays for all three marker systems (RNA, DNA and proteins). Validation of all final assays will be performed in both laboratories, Zurich and Münster, using identical sample and experimental set-ups. This two-sided approach enables us to study marker performance in more detail taking laboratory specific analysis conditions into account. Finally, we will use the data to build a robust model for predicting time since deposition of a biological trace based on the measured degradation of specific RNAs, DNAs and proteins, using the markers chosen in phase 1. The model should be applicable to all types of body fluid stains we considered in this study. The output of the prediction model will be an estimated time interval for the deposition.For the success of this ambitious project, it is on the one hand crucial to provide a complete overview of all three types of molecules (DNA, RNA, and proteins), and on the other hand to assess the reproducibility of results in different analytical set-ups. This is why collaboration between two independent laboratories is essential. Determination of TsD is an urgently needed addition to the current forensic toolbox and will aid investigators and courts of justice in assessing the relevance of biological traces. It will contribute to higher reliability in the conviction of true perpetrators as well as fast rehabilitation of the wrongfully accused.
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