i have no solid idea but would this not also depend on the chromosome? eg, Y chromosome (versus all chromosomes)? (Everything I know about DNA I learned from TV crime drama series, so...)
No, it’s way more sophisticated than that. Nowadays they are solving cold cases by finding familial matches (partial match indicating kinship) and then doing genealogies to locate family members that match age and location parameters, get dna on the sly from discarded drinks and then getting a warrant.