There are several defenses a person can raise to show that he lacked the "intent" or mens rea to commit the crime. You have heard of most of these.
1. Entrapment. This defense is primarily used in drug and prostitution cases. The idea here is that the police induced or persuaded a person to commit a criminal act they would not normally otherwise do. The key is induced or persuaded. Merely presenting a person with an opportunity to commit a crime is not inducing or persuading. Some of you may have seen -.
2. The stings on TV where the guy acting drunk parks his car on the street, leaves the keys in the car and staggers off. Criminals immediately jump in the car, start it and attempt to take off. The sting car usually has a kill switch and the car stops in the middle of the street and the car thieves are arrested. Merely making the car available to steal is NOT entrapment.
3. Self-defense. Most states allow a person to defend him or herself from attack by responding with equal force up to and including deadly force. Problems arise when the level of force is exceeded or when the victim becomes the aggressor after the attack has been foiled.
4. Necessity. This defense is rarely used today. The idea is that a person must commit one crime in order to prevent a greater crime or harm from occurring. .
5. Duress. When a person commits a crime because he has been threatened he can raise the defense of duress. Coercion simply means a threat to do some kind of harm. The threat can be to kill the actor or a member of the actor's family. He is acting under duress as long as he is committing the crime to avoid harm to himself or another. .
6. Age. In Texas juveniles (Persons under the age of 17) cannot be tried as adults. (Except in special circumstances). They are not considered to have the mens rea. .
7. Mistake. In Texas if a person has formed a belief about a fact, but is mistaken that may negate his intent. .
8. Intoxication.