If you have been charged with a crime, and the facts are sketchy, there may be good reason for your attorney to make a motion for a dismissal. There are six primary reasons why a judge may dismiss a case.
1. The complaint is based on flimsy grounds.
If you have been arrested on flimsy grounds such as hearsay, these things should not hold up in court. If the prosecutor cannot find real evidence to keep you, they will either drop the charges or they may be dismissed by the judge.
Sometimes people are intentionally over-charged with serious offenses so that they would be more likely to agree to a plea with reduced charges, and thus save the prosecutor the trouble of pursuing the case at trial. A defense lawyer could advise you (as part of his/her strategy) to wait until trial to challenge weak evidence and police/prosecutor errors. Talk with a lawyer, like Edward Galang Law for more information.
2. It has become evident that your actions were not prompted by an intent to engage in criminal behavior.
Intent to commit a crime should be evident for a charge to stick. This is another way that over-charging someone could result in charges being dismissed before or during a trial. This can happen even after jury conviction if the judge vacates the verdict because the malice or intent aspect was not evident. In the Louise Fletcher case (the nanny accused of causing shaken baby syndrome), a judge reversed a 2nd degree murder conviction for this reason.
3. Other elements of the crime are missing in the complaint.
The criminal complaint should include the list of charges to be brought against you and the reasons for the determination of probable cause. Along with intent (mens rea or "guilty mind") serious crime usually involves foreknowledge, action (actus reus), and causation resulting from the action.
Lack of foreknowledge would mean you did not know that you were committing a crime. An example would be if you were given a present and it turned out it was stolen property, or you borrowed someone's car and there were drugs hidden in it that weren't yours.
Also, you can't be convicted just for thinking about a crime; there must be some action (or deliberate inaction) involved. You could joke about hiring someone to kill your spouse, or to engage others in a conspiracy to cheat a casino. It's important that the complaint shows you took at least a first step in contacting another person and were trying to convince them to go along with your plan, or you have begun purchasing items to commit the act.
Finally, there is causation. That means your actions allegedly caused direct harm to a person, entity, or to society. If you were involved in an accident while driving intoxicated and a person died, you couldn't be convicted of reckless homicide if the cause of death was actually due to natural causes.
4. The statute of limitations has passed.
The federal statutes of limitations are five years for most crimes while each state has their own set of statutes and deadlines. The more serious the crime the longer the statutes of limitations and some crimes like murder have none.
This time period can be tolled (stopped and resumed later) if you have left the state or evidence is being tested for DNA.
Sometimes a prosecutor can go on and take you to trial so arguing that the time period has lapsed may become part of your defense.
5. The police engaged in misconduct.
If the police did not have a reasonable suspicion to stop you or probable cause to conduct a search or seizure, the evidence may not be admissible in court and your case could be dismissed if there was no other evidence.
6. Enough exculpatory evidence has been obtained to exonerate you.
As the police continue investigating your case, they could uncover enough exculpatory (defensible) evidence to make it apparent that you did not, or could not, have committed the crime. Prosecuting attorneys are required by law to turn over this evidence to your defense attorney.
As you can see, there are plenty of reasons why your case could be dismissed. However, to prepare a good defense and protect your rights, you will need to contact a criminal law attorney.