They had the DNA, they just didn't have a name and a face of who it belonged to until now.
They probably checked Matthew’s hair or saliva from a cup from his house or car and it matched to DNA in the Harrington murder.
“They had the DNA, they just didn’t have a name and a face of who it belonged to until now.”
I have to disagree. For years, police have had the face from the Fairfax rape case. They knew it was connected by DNA to the Harrington murder. Since then police have had mugshots of Jesse L. Matthew, Jr. from his repeated arrests, including for trespassing and assault. Given the ultra-high profile of the Harrington case, why in hell weren’t they checking every new arrestee for a match to that drawing, and following up any likelies with DNA tests? It is a dead ringer for Matthew. The lapse here is unforgivable.
If it doesn’t exist (though I an sure it does), someone needs to develop software to do biometric analysis on digitized mugshots and sketches of suspects, then match them. I am no computer whiz, but this seems doable, and should pay for itself in easy crime solving and prevention.