Biology Reference
In-Depth Information
is from a white Caucasian database (USA); if we recalculate with allele frequency
data representing an African American population we get a profile frequency of
3.36
×
10
−
16
, which is over 200 times less frequent than when we use the Caucasian
frequency data. In this case it is clear that the Caucasian data provides a frequency
estimate that is more conservative.
Conclusions
The methods that are employed for the correction of profile frequencies vary widely
between different judicial systems and even different laboratories within the same
judicial system. The allele ceiling principle, Balding correction, 95% confidence
interval to correct for sampling error, accounting for population subdivision using
theta, and the profile ceiling principle have all been used in forensic casework to
calculate profile frequencies. For the profile that we have been using as an example
in this chapter, the effect of the different correction methods can be seen in Table 8.3.
It should be noted that the impact of the different correction methods will vary
depending on the individual profile and the size of the allele frequency database.
The effect of the correction factors is to increase the frequency of the profile making
it more common than it may actually be. The end result of analysing a profile is
to produce a profile frequency, which is an estimate. Incorporating one or more of
the correction factors into the profile frequency estimates reduces the chances of
overstating the DNA evidence.
Further reading
Balding, D.J. (2005)
Weight-of-Evidence for Forensic DNA Profiles
, John Wiley & Sons, Ltd,
Chichester, pp. 56 - 81.
Buckleton, J., Triggs, C.M. and Walsh, S.J. (2005)
Forensic DNA Evidence Interpretation
, CRC
Press, pp. 341 - 347.
References
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Science
,
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(1963) Papers on Human
Genetics
(ed. S.H. Boyer), Prentice Hall, pp. 4 - 15.
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