For the state to prove its case in many types of criminal proceedings, it has to demonstrate that the defendant had a particular state of mind at the time of the alleged offense. For a defense lawyer, this means casting doubt on what the government says a person thought at the time. Let's look at how a criminal defense attorney might approach this question.
Most cases center on three possible ways a person might have thought of the actions they were doing. These are intentionally, knowingly or recklessly committing a crime.
Crimes of intent are ones where a person explicitly planned for a particular outcome. Although it's not the most common crime in the real world, bank robbery planning in a movie generalizes very well as an intentional crime. Short of being forced into it by someone else, there aren't a lot of scenarios where a person robs a bank without intent.
For a defense attorney, there are alleged intentional crimes committed, however, that can be explained by a client's circumstances. The classic version of this would be self-defense as an explanation for a criminal assault.
These are cases where a person allowed certain events to happen. They knew something was wrong, but they did nothing to stop it. Drug trafficking, for example, requires that the defendant knew that there were drugs in their position and that the transportation of the drugs was illegal under the circumstances.
A criminal defense law firm wants to place the pressure on the state to prove that a client did an offense knowingly. In the drug trafficking example, a criminal defense lawyer would challenge the government's attorneys to tie their client to the drugs. The state would be compelled to show some indication, such as text messages communicating with others about shipping the drugs and fingerprints on them, that they knew what was in their possession.
Some crimes arise from behavior that is reckless to the point a reasonable person would not have done what the defendant allegedly did. If a driver were speeding 25 mph over the limit in a residential area and struck a pedestrian, it would be hard for a criminal lawyer to dismiss the conduct.
From a defense standpoint, it's important to show credible explanations. A motorist might claim, for example, that their view was obstructed by bushes when they were hanging a turn prior to hitting a pedestrian.