First degree murder charges are some of the most serious that a person can face. For the defendants, finding a suitable strategy for asserting their position on the matter is imperative. Not all defenses against these charges are going to be the same. Instead, you have to think about the specific components of your case are, as well as the strength of the prosecution's case against you.
There are quite a few defense angles to use during a first degree murder trial. You can work with your defense attorney to learn more about the options that apply to your case so that you know what to expect.
Some people might use Missouri's "stand your ground" law as a defense. This will only work in very limited cases that are based on self-defense. Interestingly, you can also use a self-defense option without having to claim the stand your ground law.
You might use the fact that you were defending someone else as the basis of your defense. This would be a justified homicide, but it is also very difficult to prove. You need to be careful if you are trying to make this assertion.
Another possibility is that you were wrongfully identified as the person who did the killing. This will almost always need to be accompanied by an alibi that shows you weren't in the location of the killing when it happened.
Other possible defense options include insanity, an accident and acting in the line of duty. These all have very specific requirements so you have to find out if they meet these.