Proficiency of 38 HID-INDELS in kinship analysis and forensic parameters in a Mexican population

Introduction

Insertion–deletions for human identification (HID-INDELs) allow solving peculiar forensic situations when autosomal STRs are insufficient. Although limitations were predicted since the forensic implementation of biallelic markers, formal evaluation of these restrictions is scarce. Particularly, to define the informativity provided by HID-INDELs in kinship analysis is useful to avoid wasting work, resources, and –finally– disappointments.

Material and methods

For this reason, we analyzed the 38-plex HID-INDEL system in 25 Mexican families including father, daughter, and mother, whose kinship was previously established with 22 autosomal STRs.

Results and discussion

From genotypes of unrelated individuals, we updated allele frequencies and forensic parameters of the Jalisco state (West, Mexico), by increasing the population sample size from 62 to 112. Among the forensic a priori parameters, the Typical paternity index (PI) of the 38plex HID-INDEL system showed important differences regarding the PI and probability of paternity (W) estimated herein from real paternity cases, generally undervaluing the observed informativity of these 38-plex HID-INDEL system. Conversely, the studied HID-INDEL loci offered confident kinship conclusions based on the paternity index (PI ≥ 10,000) and probability of paternity (W ≥ 99.99%) in 68% of the standard trio cases (18/25), and only 12% of duo paternity cases (6/50) (motherless and fatherless). In fact, 14% of duo paternity cases (7/50) did not reach minimum requirements to stablish paternity (IP < 100; W < 99%).

Conclusions

We updated a Mexican population database for 38 HID-INDEL loci, and we described their proficiency from real paternity cases, detailing some limitations non-previously specified.