Suspect pulls away when I stop them?

[ztgraphix 41]

So...the only real problem im having so far is that almost everytime I pull someone over by the time I get out of my car they pull off...not in like a pursuit kind of way they just pull off and drive normal and no matter how many times I try to pull them over they keep doing it...

[ineseri 5,125]

Try turning on your siren behind the car, it sometimes forces the car to the road. 

[FCV96 806]

Have you made sure that you've stopped directly behind the vehicle and that LCPDFR prompts you to "Exit your Vehicle" at the bottom of the screen?  If it does not tell you to exit your vehicle and you get out, the AI car will drive off and it will say that you left your vehicle.