There is the matter of initial selection. If this blood turns up at a crimescene, the police know that the person involved was "Born in California since 1983",

There is the matter of initial selection. If this blood turns up at a crimescene, the police know that the person involved was "Born in California since 1983", a category which shrinks the suspect pool substantially, and can be linked via paternity and maternity to any close relative of someone born in California since 1983. If there are two or three such relatives and a precise fractional relationship can be determined (I'm assuming full sequencing), then the venn diagram of these family trees gets incredibly powerful, perhaps even powerful enough that traditional detective work is unnecessary. AFAIK nearest relative I have that was born in California since 1983 is a cousin's two children.