The first few seconds repeat. You may want to re-edit this show. 
Questions:
A boy scout knife is not that large. (Unless they were bigger back then), can you kill someone with one jab of a lil boyscout knife. (Maybe Rambo was a Boy Scout?)
Is there a test on the knife for blood? Unless you use bleach, blood usually leaves traces.
Do they compare stab wounds with the knife. (Basic CSI even for the 70s)

A good lawyer would ask these questions. 

Not believeable!!
