I think you should change "self training" to "professional training" or something similar.
Taking certain martial art classes could prove to be very valuable in case of an altercation on duty. Certainly we all realize that Karate won't do much good in the back of an ambulance. Also, Brazilian Jiu-Jitsu won't much good outside of the ambulance with several angry people waiting to stomp your head in if you were to take someone to the ground.
LEO training is based off several things; Hapkido, Brazilian Jiu-Jitsu, Akido, Judo, and a mix of other tricks that are proven to work but loosely based of a martial art of some type. But unless you practice these moves several times, get your timing down and muscle memory down, and being able to recognize different options during an altercation - you're left with your own survival skills.
Personally, when I was in paramedic class I joined a gym and began taking Brazilian Jiu-Jitsu. I was concerned with not being able to defend myself or subdue someone if I was ever in that event (I was 5'9 165lbs then) Fortunately, we shared the space with a boxing club and my instructor also enjoyed and made us practice kick-boxing, muay thai, and boxing so I was exposed to striking as well as grappling. I enrolled back into Brazilian Jiu-Jitsu in December and for being 8 years older, heavier, and out of shape; it's been murder! I don't do it for self-defense, I do it because I truly love the sport and the fitness aspect of it.
Bottom line - training is great but common sense and instinct will serve you best by not getting into a dangerous situation.