I take it you will shoot this yourself. Just be aware that this is not the correct script format if you were submitting to a studio. You might want to get a copy of David Trottier's Screenwriting Bible to understand that process. Also, there is a free software program called CeltX which will not only help with the screenwriting process, but has some useful features for actually arranging your shoot.
As for the script, I thought it started well then kind of slid off into silliness. The dialogues also felt forced rather than natural. In several places you use one of them to get information to explain the scene to the audience. You want to use as little 'exposition by proxy' as possible. The information should be obvious to the audience or the character should just dish. To have the back and forth between the partner--"Did ya see that?" "What?" "There ... the blood." "Uh, what about it?" ... 1. It doesn't really do anything except waste time. 2. The audience sees the blood, so make it relevant rather than point attention to it. Something like "The blood spot ... the pattern suggests a downward thrust." "So you're thinking the attacker was taller than him." To the point and relevant.
Finally the ending was confusing.
At the end of scene 14, Johnson falls into the puddle. McFly stuffs his body ('ex-partner') into the back of his car.
Scene 15, Johnson stands up from the puddle. How'd he jump from the car back to the puddle? Always check your continuity!
It needs some work because it's difficult to read as formatted. The action descriptions are lost between the dialogue lines. I think it's a good start for your own filmmmaking purposes.
