Identification Strategy of Biological Half Sibling Relationship

Area of Science:

• Forensic Genetics
• Population Genetics
• Statistical Genetics

Background:

• Accurate identification of familial relationships is crucial in forensic science.
• Distinguishing half siblings from full siblings and unrelated individuals presents unique challenges.
• Existing methods like Identity by State (IBS) have limitations in precision.

Purpose of the Study:

• To compare the application value of the likelihood ratio (LR) method and the identity by state (IBS) method for half sibling identification.
• To provide a reference for establishing standards in half sibling relationship identification.
• To determine the optimal genetic markers and their quantity for reliable relationship inference.

Main Methods:

• Computer simulations were used to model full sibling, half sibling, and unrelated pairs.
• Cumulated Identity by State (CIBS) scores and cumulative LR parameters were calculated.
• System efficiency of LR and IBS methods was compared across various genetic marker combinations and accuracies.
• Curve fitting was employed to estimate the minimum number of genetic markers required for accurate identification.

Main Results:

• Computer simulations reliably mirrored results from actual cases.
• The LR method demonstrated superior system effectiveness compared to the IBS method under identical conditions.
• The study determined the number of genetic markers needed to achieve 0.95 or 0.99 system effectiveness for half sibling identification.

Conclusions:

• The likelihood ratio (LR) method is recommended over the identity by state (IBS) method for distinguishing half siblings.
• The number of genetic markers required should be estimated based on the specific identification type and population data.
• Implementing the LR method with appropriate marker selection ensures reliable forensic identification of half siblings.