Biomedical subjects

J Buckleton

Publications and source records attributed to J Buckleton.

5 recordsLinked to original sources

PubMed1998

Combining a continuous Bayesian approach with grouping information.

When someone breaks glass a number of tiny fragments may be transferred to that person. If the glass is broken in the commission of a crime then these fragments may be used as evidence. A Bayesian interpretation of this evidence relies on, among other things, the forensic scientist's ability to assess the likelihood that the glass recovered from the suspect may have come from more than one source. This paper will examine the effect of including this information in the interpretation. We envisage working towards a system whereby the information loss that occurs during the normal casework activities of sample selection and glass fragment grouping is quantified.

Algorithms↗

PubMed1998

Interpreting simple STR mixtures using allele peak areas.

Although existing statistical models can interpret mixtures qualitatively based upon the alleles present, the use of automated sequencers opens the opportunity to take account of quantitative aspects embodied by the peak area. One step in understanding simple mixtures consisting of just two donors is to estimate the mixture ratio. This is relatively easy to do when four-allele mixtures are evident at a given locus. However, if the mixture consists of three or fewer alleles, the process it is not straightforward. We demonstrate that mixture estimates are consistent across all loci in a multiplex system. Once the mixture ratio is known, then the expected peak areas for any given combination of alleles can be estimated using a simple spreadsheet analysis.

Alleles↗

PubMed1997

Interpreting DNA mixtures.

The interpretation of mixed DNA stains is explained in the context of likelihood ratios. The probabilities for the mixed-stain profile are evaluated under alternative explanations that specify the numbers of contributors and the profiles of any known contributors. Interpretations based simply on the frequencies with which random members of a population would not be excluded from a mixed-stain profile do not make use of all the information, and may overstate the strength of the evidence against included people. The effects of the numbers of contributors depends on whether all the alleles at a locus are present in the mixed stain. A general equation is given to allow likelihood ratios to be calculated, and includes the "2p" modification suggested by the 1996 NRC report. This modification is not always conservative. A computer program to perform calculations is available.

Alleles↗

PubMedDate not supplied

A continuous model for interpreting the positions of bands in DNA locus-specific work.

A simple but rigorous approach is offered for evaluating the evidential value of single locus DNA autoradiographs. This approach does not use a binning technique and it does not treat alleles as discrete variables. Instead, the allele distribution is considered to be continuous. The variation between two comparable bands is assessed using previously determined experimental parameters. The Bayesian treatment leads to an expression of the "quality of a match".

Alleles↗

PubMedDate not supplied

Sampling in forensic comparison problems.

When someone breaks glass a number of tiny fragments may be transferred to that person. If the glass is broken in the commission of a crime then these fragments may be used as evidence. If a large number of fragments are recovered from the suspect, then it may be more efficient for the forensic scientist to examine a subset of these fragments. Such sampling incurs information loss. This paper will derive an expression that allows a partial quantification of this loss. The loss of such information due to the examination of a subset of recovered material arises with many forms of evidence.

Forensic Medicine↗