Genealogy Explainer

Welcome to this short explainer on genetic genealogy.

CODIS is the “Combined DNA Index System.”

Agencies obtain a DNA profile from a victim, from a piece of evidence, or a suspect and these are compared to samples held in CODIS to see if there is a match.

The collection and entry of samples did not become commonplace until the 90s and there are lots of prisoners whose details were never recorded, so the database is not complete.

There are now lots of public databases – such as

These databases use a slightly different type of DNA sample, called snips. This is the same method which can also provide pheenotyping, which can tell us eye and hair colour for example.

Authorities can search these genealogical databases, looking for matches which are not held in CODIS.

This is a very useful tool, and led to the capture of the Golden State Killer when his previously unmatched CODIS samples were fed into GEDmatch and a close relative was identified, leading to his arrest and conviction.

Genetic genealogy is a powerful and exciting development.

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In The Blood

In The Blood: DNA testing truly is a complex and, for many, controversial topic area, set against a backdrop of global differences in approach to fundamental rights and freedoms which can make discussions like this too hot to touch. Nonetheless, there are still these much bigger discussions to be had around the way we use the power of DNA to prevent harm in society and that’s the real challenge here – getting to a point where the basic premise of the discussion is understood in its simplest form: a problem to solve. For me the conversation starts with that poor girl in the field. She deserves to be known. She deserves peace. In a world where her DNA was attributable to her, nearly forty years wouldn’t have passed. But sometimes solving one problem can create many more conflicts and it is important to appreciate that fully. This is the thing about investigative work. Sometimes, there’s just no easy answer. But we still have to talk about even the things we might not want to, calmly and rationally, because an unexplored avenue might be the one where the right answer lies.


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