Pevid2 {forensim}R Documentation

Conditional profile probabilities

Description

Calculates the probability of observing a set of DNA profiles conditional on a given hypothesis specifying who were the contributors to the observed profiles. All the individuals involved in the analyzed case are assumed to come from the same subpopulation with a given coancestry coefficient.

Usage

Pevid2(stain, freq, x, T = NULL, V = NULL, theta = 0)

Arguments

stain vector of distinct alleles (from one specific locus) found in the crime sample.
freq vector of the corresponding allele frequencies in the global population
x the number of unknown contributors to the mixture
T object of class genotype (package genetics), or a vector of strings where each string contains two alleles separated by '/', corresponding to one known contributor. The length of the vector equals the number of known contributors. Default is NULL.
V object of class genotype (package genetics), or a vector of strings where each string contains two alleles separated by '/', corresponding to one known non-contributor. The length of the vector equals the number of known non-contributors. Default is NULL.
theta a float in [0,1[. theta is equivalent to Wright's Fst. In case of population subdivision, it allows a correction of the allele frequencies in the subpopulation of interest

Note

Please note that the Pevid2 function is an improved version of the Pevid.gen function from the forensic package by Miriam Marusiakova (which explains the 2 in the function name). Pevid2 calls external functions in C code.

Author(s)

Hinda Haned haned@biomserv.univ-lyon1.fr

References

Curran JM, Triggs CM, Buckleton J, Weir BS. Interpreting DNA Mixtures in Structured Populations. J Forensic Sci 1999;44(5): 987-995

See Also

LR, RMP

Examples

# A rape case in Hong Kong (Hu and Fung, Int J Legal Med 2003)
# The stain shows alleles 14, 15, 17 and 18 at locus D3S1358.
stain=c(14,15,17,18)
# suspect's profile: "14/17"
suspect<-"14/17"
# victim's profile: "15/18"
victim<-"15/18"
# corresponding allele frequencies 
freq<-c(0.033,0.331,0.239,0.056)

# Prosecution proposition: Contributors were the victim and the suspect 
# defence proposition: Contributors were the victim and 1 unknown contributor
# from the same subpopulationas the victim
# Evaluation of the defence proposition, in case of independence between alleles
Pevid2(stain, freq, x=1, T = victim)

# note that if theta=0, the suspect's profile plays no role in the calculation
#and the same result is obtained
Pevid2(stain, freq, x=1, T = victim, V = suspect)
# In case of allele dependencies, measured by theta=0.03
Pevid2(stain, freq, x=1, T = victim, V = suspect, theta = 0.03)


[Package forensim version 1.1-1 Index]