Here's my problem...if they have all of this blood evidence that points to Raven, yet there has not been an arrest, there has to be something standing in the way.
1) TOD eliminates Raven, his alibi holds up, so he couldnt have been there when the crime was comitted, meaning the story of how the blood got on doors is accurate.
2) No blood cast-off patterns on ravens clothes, only blood stains, indicating he indeed held her, but did not stab her.
3) There is another POI they are investigating at this time.