Why didn't the blood match up with Wells in Season 1 Episode 13?

Question

In "The Nuclear Man", Barry and Cisco find blood splatter on the wall of the old Allen home and it's tested against samples they have, including specifically against Professor Wells, as Barry believes it belongs to the Reverse Flash. However, it comes up negative for Wells. Why wasn't Wells identified?

Answer 1

The sequence of events for Eobard Thawne's time travel is that he goes back in time, kills Nora (while fighting The Flash) and then, realizing that his connection to the Speed Force is fading, he arranges for the death of Professor Wells and uses future technology to take on Wells's appearance and identity. Presumably, whatever technology he used also changed his body to match any existing biometric samples for Dr. Wells. Therefore, the DNA of the blood on the wall, from the original Eobard Thawne, is likely not the same as that of the body of Professor Wells that he now wears.

Answer 2

Well it is basically simple, you can’t find a person in the current database if they’re from the future, because if they’re from the future then they can’t be detected in the criminal database since they aren’t from that time and haven’t been entered into the crimson database of that time, the criminal database only has records on everyone from the time it was made, so it can’t detect someone if they’re from the future, or not from the time when the people were entered in the database, basically if you’re confused, it’s basically like you can’t know what an orange tastes like or looks like if you’ve never seen or tasted an orange, the criminal database works the same way, it can’t detect someone who hasn’t been entered into the database if they’re from the future