Estimation of the Age of Body Fluid Stains Using RNA Degradation and a Novel qPCR Approach

BACKGROUND

Forensic laboratories frequently quantitate the amount of human genomic DNA recovered from evidentiary biological fluid samples. Additionally, forensic experts are often called into court to testify as to when a particular biological fluid sample was deposited at a crime scene. The time of deposit of a biological fluid sample remains a critical component of DNA experts’ testimonies. Current methods for quantifying and/or estimating the age of a biological fluid sample utilize two transcripts: one in which the amount of the transcript is expected to change over time, and another in which the amount of the transcript is expected to remain stable. This dual monitoring of transcripts allows to normalize the quantity of the changing transcript by comparing to the quantity of the stable transcript among biological replicates. However, one primary problem with the current methodology is that stochastic effects can occur during the reverse transcription reaction and qPCR cycles thereby negatively affecting the reproducibility of estimates for cDNA copies of the RNA transcripts present in a particular biological fluid sample. This problem may be magnified when a more abundant transcript is not being affected as significantly as a less abundant transcript.

SUMMARY OF TECHNOLOGY

The present invention allows to more accurately estimate the time when a biological fluid was deposited at a crime scene and to quantify nucleic acids in a particular biological fluid sample. Having performed detailed analysis of transcripts behavior in ex vivo body fluid stains, OSU investigators have measured kinetics of RNA degradation process to develop a more reliable method for estimating the age of a stain at a crime scene. By assessing degration profiles of a vast array of mRNA molecules in various biological samples (e.g., blood, saliva, vaginal fluid, semen), our researchers have identified particular transcripts and groups of transcripts that disappear with kinetics that correlates with sample age. The technology can thus be particularly useful for forensic applications.

POTENTIAL AREAS OF APPLICATION AND MAIN ADVANTAGES

• This technology produces more accurate estimates than those achieved by conventional forensic methods because the present invention minimizes errors from stochastic effects e.g., during reverse transcription
• The technology enables assessment of mRNA degradation kinetics in predictable and reproducible manner
• Different degradation rates of our indentified transcripts allows to fine-tune the technology for detection of young and old samples
• User-friendly data analysis tool have been developed to produce time estimates
• The technology can be readily deployed because it only requires instrument platform commonly available at forensic DNA laboratories

STAGE OF DEVELOPMENT

• Proof-of-concept