forensim (version 2.0)

dropDB: Calculates LR allowing for drop-out and drop-in

Description

This function wraps up David Balding's code.

Usage

dropDB(dataBase, DNA, dropHetero = 0.05, alpha = 0.5, 
dropIn = 0.05, rel = c(0, 0)/4, maxUnknown = 1,
 adj = 0, fst = 0)

Arguments

dataBase

An R data frame with header 'marker allele count' with columns giving the names of the marker and the allele and the count (the number of occurences of the allele) in the database.

DNA

An R data frame with header 'MarkerSource A1 A2 A3 A4' There are four lines for each marker corresponding to alleles for the (i) the mixture (ii) known contributor (if there is one) (iii) the defendant and (iv) drop-out alleles. The names and order of

dropHetero

Probability heterozygous drop-out

alpha

Balding and Buckleton's alpha-parameter defining relation between homozygous and heterozygous drop out probabilities.

dropIn

Drop-in probability.

rel

A vector of length 2 giving the IBD=1 and IBD=2 probabilities and so c(0,0) corrresponds to unrelated contributors.

maxUnknown

The maximum number of unknown contributors under the defence hypothesis. Possible values 1 or 2.

adj

Parameter to adjust for sampling adjustment. Balding uses 2.

fst

Parameter to adjust for coancestry. Balding recommends values between 0.01 and 0.05.

Value

• Marker name, LR and numerator and denominator of LR.

References

Balding DJ, Buckleton J, Interpreting low template DNA profiles, Forensic Science International: Genetics, 4: 1-10, 2009, doi: 10.1016/j.fsigen.2009.03.003. http://www.zebfontaine.eclipse.co.uk/djb.htm

Examples

#First output column of Table 1 in Balding and Buckleton:
data(Bates.Database);data(Bates.DNA)
dropDB(Bates.Database,Bates.DNA,dropHetero=0.05,alpha=0.5,dropIn=0.00,rel=c(0,0)/4,
maxUnknown=1,adj=2,fst=0.02)
#First output column of Table 3 in Balding and Buckleton:
data(CaseY.Database);data(CaseY.DNA)
dropDB(CaseY.Database,CaseY.DNA,dropHetero=0.5,alpha=0.5,dropIn=0.05,rel=c(0,0)/4,
maxUnknown=1,adj=2,fst=0.02)