LR: Likelihood ratio for DNA evidence interpretation (2): a...
In forensim: Statistical tools for the interpretation of forensic DNA mixtures

Description Usage Arguments Author(s) References See Also Examples

LR Allows the calculation of likelihood ratios for a piece of DNA evidence, for any number of replicates, any number of contributors, and when drop-in and drop-out are possible.

1	LR(Repliste, Tp, Td, Vp, Vd, xp, xd, theta, prDHet, prDHom, prC, freq)

`Repliste`	vector of alleles present at a given locus for any number of replicates. If there are two replicates, showing alleles 12,13, and 14 respectively, then `Repliste` should be given as c(12,13,0,14), where the 0 is used as a separator. An empty replicate is simply 0. For example, replicates (12,13) and and one empty replicate must be given as: c(12,14,0,0).
`Tp`	vector of genotypes for the known contributors under Hp. Genotype 12/17 should be given as a vector c(12,17) and genotypes 12/17,14/16, should be given as a unique vector: c(12,17,14,16).
`Td`	vector of genotypes for the known contributors under Hd. Should be in the same format as Tp. If there are no known contributors under Hd, then set Td to 0.
`Vp`	vector of genotypes for the known non-contributors (see References section) under Hp. See `Tp` for format.
`Vd`	vector of genotypes for the known non-contributors (see References section) under Hd. Should be in the same format than Vp, if empty, set to 0.
`xp`	Number of unknown individuals under Hd. Set to 0 if there are no unknown contributors.
`xd`	Number of unknown individuals under Hd. Set to 0 if there are no unknown contributors.
`theta`	thete correction, value must be taken in [0,1)
`prDHet`	probability of dropout for heterozygotes. It is possible to assign different values per contributor. In this case, `prDHet` must be a vector, of length the number of contributors in T + x, and the probabilities must be given in this order. if the probability of dropout for T is d1, and for the unknown is d2, then `prDHet`=(d1,d2). In case T is not a heterozygote, the given vector must still be of length length(T) +x, but the given value for T does not matter, because it won't be used, the value in prDHom is used instead. This is a bit ad hoc and an improvement is currently under development.
`prDHom`	probability of dropout for homozygotes. See description ofr argument `PrDHom`.
`prC`	probability of drop-in applied per locus
`freq`	vector of the corresponding allele frequencies of the analysed locus in the target population

Hinda Haned contact@hindahaned.info

Gill, P.; Kirkham, A. & Curran, J. LoComatioN: A software tool for the analysis of low copy number DNA profiles Forensic Science International, 2007, 166(2-3), 128-138

Curran, J. M.; Gill, P. & Bill, M. R. Interpretation of repeat measurement DNA evidence allowing for multiple contributors and population substructure Forensic Science International, 2005, 148, 47-53

LRmixTK

#load allele frequencies
library(forensim)
data(ngm)
#create vector of allele frequencies
d10<-ngm$tab$D10
# heterozygote dropout probability (resp. homozygote) is set to 0.2 for all
# contributors (0.04 for homozygotes) 
LR(Repliste=c(12,13,14),Tp=c(12,13),Td=0,Vp=0,Vd=0,xd=2,xp=1,theta=0,prDHet=c(0.2,0.2),
prDHom=c(0.04,0.04),prC=0,freq=d10)