Developing allelic and stutter peak height models for a continuous method of DNA interpretation

The variability in likelihood ratios due to different mechanisms

“…software STRmix TM [10][11][12]. An intended outcome of standardisation processes is to reduce the variability within each region.…”

Probabilistic characterisation of baseline noise in STR profiles

“…Interpretation methods that utilise peak height or area information, rather than the binary information of whether a peak height or area exceeds a threshold or not, have garnered much attention, and a variety of fully-continuous interpretation platforms have been developed [9][10][11][12][13][14][15][16].…”

A signal model for forensic DNA mixtures

“…In general, it increases with increasing repeat number. In [10], [11] it was reported that the longest uninterrupted sequence (LUS) in an allele might be more appropriate than the repeat number of an allele to describe the increase of the stutter proportion. Our approach to model stutter is linear in the sense that the stutter peak height is always a fixed proportion of the hypothetical allelic peak height before stutter, according to (2).…”

“…Further, a second threshold, the stochastic threshold, may be used as a tool to detect the presence of allelic peaks [7]. The traditional way to counter the effect of stutter is to apply a stutter ratio threshold, where the ratio is calculated by dividing the height of the peak in stutter position by the height of the allelic peak [8]- [11]. Other effects are generally not treated specifically [12].…”

“…Applying thresholds during analysis has the drawback that information is lost. For that reason, continuous methods, where fewer or no thresholds are used, have been developed [11], [13], [14]. In these methods the full variability in the peak heights is taken into consideration, which leads to a soft decision instead of a hard limiting.…”