forensim (version 1.1-4)

Pevid2: 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.

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-contribut

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

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 subpopulation as 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)