The morning session, chaired by Brian Rankin, began with a presentation by Matthew Greenhalgh from Cellmark Forensic Services. Matthew presented 'Low Template DNA Analysis: Opportunities and Challenges'. The presentation reviewed the changes in DNA analysis testing sensitivity since Multi Locus Probes (MLPs) in 1987, from starting material of 5-10 µg, to high sensitivity Short Tandem Repeat (STR) testing from less than 250 pg of DNA. The presentation then highlighted some of the detail contained within Professor Caddy's report including the background to the review into low template DNA (LT-DNA) analysis and the issues that were associated with the technique from the crime scene, to the laboratory and then the presentation of LT-DNA evidence in court.
Matthew then proceeded to discuss the alternative approaches to LT-DNA analysis which exist, including increasing the PCR cycle number or post-PCR modifications to increase the signal to noise ratio during electrophoresis. Increasing the PCR cycle number from 28 to 34, or Low Copy Number (LCN) analysis, was said to increase the sensitivity of the analysis but with an associated increase in the likelihood of over-amplification of artefacts and heterozygote imbalance. Enhancing the analysis of PCR products by modifying them post-PCR was said to produce similar levels of sensitivity to 34-cycle LCN analysis but that heterozygote imbalance and stutter peak ratios were unchanged from original 28-cycle results. The enhancement process was proposed to take place in two phases: PCR product purification by de-salting and the removal of unincorporated dNTPs and primers was undertaken in phase one and phase two was the injection of more PCR product at the electrophoresis stage. After some clear examples of the positive effects of post-PCR enhancement on the quality of DNA profiles, Matthew mentioned some of the caveats which should be applied in all cases where LT-DNA analysis was employed. These included the inability to state the origin of material or the method of transfer from which the profile was derived. After clarification that the