Combining artificial neural network classification with fully continuous probabilistic genotyping to remove the need for an analytical threshold and electropherogram reading

• NCJ Number: 305600
• Journal: Forensic Science International-Genetics Volume: 62 Dated: 2023
• Author(s): Duncan Taylor; John Buckleton
• Date Published: January 2023
• Grant Number(s): 2020-DQ-BX-0022
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)
• Award: Population Genetic Issues for Forensic DNA Profiles

Annotation

This project features a process that combines artificial neural network classification with fully continuous probabilistic genotyping to remove the need for an analytical threshold and elerctropherogram reading.

Abstract

Standard processing of electrophoretic data within a forensic DNA laboratory is for one (or two) analysts to designate peaks as either artefactual or non-artefactual in a process commonly referred to as profile ‘reading’. Recently, FaSTR™ DNA has been developed to use artificial neural networks to automatically classify fluorescence within an electropherogram as baseline, allele, stutter, or pull-up. These classifications are based on probabilities assigned to each timepoint (scan) within the electropherogram. Instead of using the probabilities to assign fluorescence into a category they can be used directly in the profile analysis. This has a number of advantages; increased objectivity in DNA profile processing, the removal for the need for analysts to read profiles, the removal for the need of an analytical threshold. Models within STRmix™ were extended to incorporate the peak label probabilities assigned by FaSTR™ DNA. The performance of the model extensions was tested on a DNA mixture dataset, comprising 2–4 person samples. This dataset was processed in a ‘standard’ manner using an analytical threshold of 50rfu, analyst peak designations and STRmix™ V2.9 models. The same dataset was then processed in an automated manner using no analytical threshold, no analysts reading the profile and using the STRmix™ models extended to incorporate peak label probabilities. Both datasets were compared to the known DNA donors and a set of non-donors. The result between the two processes was a very close performance, but with a large efficiency gain in the 0rfu process. Utilising peak label probabilities opens up the possibility for a range of workflow process efficiency gains, but beyond this allows full use of all data within an electropherogram. (Publisher abstract provided)