How to Find a Killer on Ancestry

Andrew Gaertner
7 min readOct 18, 2022

Or a birth parent for an adoptee

Photo by kat wilcox on Pexels

Ok. I have never found a killer on But I know I could if I had the right information. I have found birth parents for people by using the same techniques forensic genealogists use to find killers or rapists. I would say it is fun if it weren’t such a serious undertaking. Here is how I do it.

The first thing I need to find a birth parent is for my client to take an DNA test. Then we wait an interminable six weeks for the results so I can go to work.

Once the results come in, we need to create a blank family tree for my client.

The Ancestry DNA results come in three sections. The middle section of the DNA results, called “DNA Matches,” is by far the most important for finding people. This section displays all the people who have taken the test who also share sections of DNA with the person tested. It will rank them in order of how much shared DNA they have, from most to least. To catch a killer or find a birth parent, this is the starting point.

Let’s imagine we have DNA evidence from a crime scene. The first step would be to get DNA samples from the victim, the first responders, and others who may have contaminated the crime scene evidence. Then once those people are ruled out, we submit the unknown crime scene DNA to and other genealogy websites and wait for the results.

Once we have results, we treat the sample from the crime scene just like a client who is looking for their birth parents.

Looking at the “DNA Match,” we might have literally hundreds of people who are related to the person. Sometimes we can get lucky and find a close relative like a brother or parent who has already submitted a sample. Most of the time we don’t get so lucky. Usually, the closest person on the list is the equivalent of a 2nd or 3rd cousin.

Many of the DNA matches choose not to be anonymous. In fact, these people post their whole family tree for everyone to see. It is part of the genealogy world for people to publicly share their trees as part of a collective effort to help other people build their trees. I do this with my tree of over 10,000 people, and I sincerely appreciate other people who choose to make their trees public.



Andrew Gaertner

To live in a world of peace and justice we must imagine it first. For this, we need artists and writers. I write to reach for the edges of what is possible.