of the suspect when he was younger and this led to virginia detectives to the new york home of stephen smerkf fairfax county police department. chief, thank you so much for being with us. obviously a terrible case. but good news there is an ending here. explain how these detectives tracked smerk down with dna and how this sketch played a role. >> well thank you for having me. that sketch is aize maing and that sketch was not drawn by an artist. it was generated by genetic research genealogy. it is an amazing cool. we saw several cases in the past couple years based on familiar matches. we collected a good dna sample back in 1994 to we have a dna profile that sat in a facial data base and almost 30 years later, a relative of stephen smerk was hit upon. so we knew that we didn't have our killer necessarily, but we had someone related to our killer and that is when our cold case detectives decided to take a trip up to new york. >> and explain that. so that leads to a sketch. how do you find the person to then go to his house? >> you look at who that person is related to and you see if that pers