Child Body Identification Trick

  1. The problem
    1. Given DNA profiles for Mother (M), Father (F), and a body (C) suspected to be their child, what is the likelihood ratio LR supporting relationship versus unrelated?

  2. Strategy
    1. Solve the problem in terms of two related problems.

    2. Compute the trio paternity index PI for the M-C-F trio, as if F were an alleged father.
    3. Compute the duo maternity index MI relating M-C as parent-child or unrelated
    4. The desired LR=PI•MI

  3. Why does it work?
    1. Consider these 3 hypotheses: In terms of these hypotheses, note that or in formulas: from which obviously LR=PI•MI as claimed.

  4. What good is it?
    1. In DNA•VIEW you can of course directly compute the body ID LR using the Automatic Kinship Case program. However, for an irregular suitation involving possible mutation or null alleles, the kinship calculation is not as sophisticated and accurate as the calculation done by the special-purpose Paternity Case calculation. Therefore it can be advantageous to do the body ID calculation in two steps using Paternity Case.