Not excuses. Just affirmation of a lack of evidence. Police have all but said THIS IS OUR GUY without having any forensic or eyewitness testimony that she got in his car with him! You want Matthew to talk to the police when in his mind they've already convicted him?
The evidence is still being tested, so its impossible to say there isn't any. If , for example, the found dried blood in the car, it would take some time to complete DNA testing.