DNA testing can positively exclude someone as the perpetrator of a crime. But because it's so expensive, and people charged with crime are often poor and dependent on court-ordered funding for their defenses, oftentimes it isn't done.
If you believe you or someone you know has been wrongfully charged with a crime, make sure you ask your lawyer to seek out any possible DNA evidence for testing, and if necessary, to ask or "pettition" the court to pay for it.
Of course, you may have other defenses to the charge. In order to determine what defense you might raise, and your chances of succeeding, you should contact a criminal defense lawyer in your area who's experienced in defending charges of sexual assault against minors.
A valid entrapment defense has two related components:
The defendant has the initial burden of proving the government induced him to commit the crime. Then the burden shifts to the prosecution to prove beyond a reasonable doubt that the defendant was predisposed to commit the crime.
Entrapment occurs when the criminal design starts with law enforcement officers, who plant the idea to commit the crime in the mind of an innocent person, and then convince him to do the crime so they can prosecute him.
"Predisposition" focuses on whether the defendant was an unwary innocent who, but for the inducement of the officers, wouldn't have committed the crime.
The fact that law enforcement agents provide the opportunity or place for the crime doesn't add up to entrapment. It's only entrapment when the idea for committing the crime is planted in the defendant's mind by law enforcement. For example, there's generally no entrapment where a defendant, while in an area known for illegal drug activities, is arrested after trying to buy illegal drugs from an undercover officer.
While the law on self-defense usually varies by state, generally a person is justified in using physical force when it's necessary to defend himself or a third person from what he reasonably believes the use or imminent use of unlawful physical force by the other person.
How much force can you exert in self-defense? Only the amount you reasonably believe is necessary to defend yourself or another person from an unlawful use of force.
Can you ever respond to an attack or threat of an attack by using deadly force? Deadly physical force may be used only if you reasonably believe:
You aren't justified in using physical force if you provoke the use of unlawful physical force by another person. And you can't justify your use of force if you're the initial aggressor - meaning you started the fight - unless you stop using force first and the other person continues using force.
Some states have "make my day" or "castle" laws that let people use deadly physical force against an intruders they believe have unlawfully entered their home with the intent to commit a crime once inside. These laws assume that citizens have a right to expect absolute safety within their homes.
Some states also allow defendants to argue that that they understood their behavior was criminal but were unable to control it. This is sometimes called the "irresistible impulse" defense.