8127/frame/fm

LR 1. Assuming the presence of Boyfriend in both hypotheses
LR 2. Assuming the absence of the Boyfriend
The results can be summarized as follows: The probability of the evidence
under Hypothesis 1, the boyfriend and the suspect, is many orders of mag-
nitude greater than any of the others. How should this be expressed? We take
LR 1 as an example. We could say either of the following:
• The evidence profile is at least 1.5 billion times more likely to be of
the type seen if the boyfriend and the suspect are the donors, than if
the boyfriend and any other random man are the donors.
• The probability of someone other than the suspect having the requisite
profile to complete the observed mixture, assuming the boyfriend is
present, is 1 in 1.5 billion.
* The details of these calculations are given in Appendix E. We use the Caucasian popu-
lation frequencies for the example.
P E
Boyfriend + Suspect
(
)
P E
Boyfriend + random man
(
)
---------------------------------------------------------------------------
1.5 billion
=
P E
Suspect + random man
(
)
P E
two 2
( )
random men
(
)
---------------------------------------------------------------------
45,000,000
=
8127/frame/ch06 Page 146 Friday, July 21, 2000 11:47 AM

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Classification, Identification, and Individualization
147
To illustrate the value of this approach, the RMNE is also calculated in
Appendix E. By ignoring the additional evidence (
E
) provided by the analysis,
that two and only two donors are present, and the information (
I
) about the
case, that is, that the victim indicates a consenting intercourse with a named
donor whose sample is available, at least three orders of magnitude of infor-
mation are lost.