Duo / Motherless Case
Definition
A paternity test in which the mother's profile is unavailable; the PI denominator must integrate over all possible maternal allele contributions from the population, generally reducing the CPI relative to the trio configuration.
- Field
- Forensic paternity testing
- Missing profile
- Mother
- Statistical effect
- PI denominator integrates over population allele frequencies
- Result
- Generally lower CPI than a trio case
Common questions
Why does a duo case usually produce a weaker statistical result than a trio case?+
Without the mother's genotype, the calculation must account for every possible maternal allele contribution weighted by population frequency, which adds statistical uncertainty. A trio case removes that uncertainty because the mother's actual contribution is known directly.
Does the absence of a maternal profile make a duo paternity result inadmissible?+
No, duo analysis is a standard and accepted method in paternity casework when the mother is unavailable, deceased, or uncooperative. The result is simply reported with the appropriately adjusted, typically lower, combined paternity index.
Related terms
- Combined Paternity Index (CPI)
- The product of all individual paternity indices across all marker systems tested. Assumes independence of the marker systems. The CPI is a...
- Familias
- Open-source kinship LR software developed in Norway, the reference platform for ISFG kinship workshops and used operationally by forensic labs in Sweden,...
- Inbreeding Coefficient (F)
- The probability that two alleles at a locus in an individual are identical by descent, reflecting population consanguinity. Non-zero F values affect...
- NamUs
- National Missing and Unidentified Persons System (US), a national database cross-matching PM profiles of unidentified remains against AM kinship reference profiles; has...
- Paternity Index (PI)
- A likelihood ratio that compares the probability of the observed serological profile if the alleged father is the biological father to the...
- Sibling Likelihood Ratio (SLR)
- Likelihood ratio comparing the probability of the observed genotype data if two persons are full siblings versus unrelated. Values much greater than...
- Track Child
- India's Missing Persons and Children portal managed by the Ministry of Women and Child Development and NCRB, the domestic framework through which...