Understanding Basics of Criminal Law | By Colin Bell
Posted 08/22/2022 in Criminal Defense by Colin Bell

Understanding Basics of Criminal Law

For all the endless parade of movies, TV shows, books, podcasts, and more, about cops and robbers, you’d think that everyone had a mastery of criminal law: We all should be ready to sit as second chair counsel for a criminal trial. But the fact is that most cop and courtroom dramas barely touch on criminal law. And even those that do often take liberties with the law for the sake of the story.

So let’s discuss some of the real basics of criminal law. Understanding them can be helpful whether you are a defendant seeking criminal defense, a victim needing assistance, or a citizen who wants to be better informed about criminal justice. 

Criminal Law vs. Civil Law

It’s vital to understand the difference between a criminal and civil case. 

In a criminal case, a prosecutor (an attorney who works for the state) represents the state when they bring a case against a defendant who is alleged to have participated in a crime. The idea is that a crime is an act that has injured the entire state, and therefore the state must defend itself and society’s members at large. 

Of course, many crimes (like theft or murder) cause harm to a person or an entity. Therefore, in recent years, there has been a push for victims to have more of a voice in the process. Victims may receive legal representation of their own. Some testify in sentencing proceedings and so on. But none of that changes the fact that the prosecutor represents the state’s interests—not the victim’s. 

Given the seriousness of having defendants injure the state (i.e., society as a whole), the state can punish convicted defendants with incarceration.

A felony describes a serious crime that is punishable by a sentence in prison of a year or more. A misdemeanor is a lesser crime with a jail sentence that must be 364 days or fewer. 

A state can also order additional forms of punishment: 

  • probation
  • financial fines and fees (including court costs)
  • restitution
  • other restrictions on behavior that may relate to the crime (ignition interlock devices on a car after a drunk-driving conviction, curfews for juvenile offenders, etc.) 

Furthermore, criminal convictions can strip someone of their rights relating to their membership in society (e.g., they can lose the right to vote). 

Because of these severe consequences, the state must meet a very high bar to win a conviction. The state prosecutor must prove the case “beyond a reasonable doubt.” The judge or jury must be certain that the defendant committed the crime, and there is no other legitimate explanation. 

On the flip side, defendants are not obligated to prove they are innocent of the crime. That is why if a defendant is convicted, they are “guilty.” But if they are not, they are “not guilty.” They are not proven “innocent.” 

The standards are much different in a civil case. There, a plaintiff—a person or entity—files suit against a defendant, seeking compensation for the harm the plaintiff claims the defendant has caused them. If a plaintiff wants representation in court, they must hire an attorney. 

Depending on the civil case, the plaintiff might ask for the return of their property, but usually, the plaintiff demands cash compensation. Civil defendants do not face jail time. 

Because the stakes are lower in a civil case, the burden of proof is lower. To win a civil case, a plaintiff must prove only their case by a “preponderance of the evidence,” i.e., there’s a 50% chance or greater that the defendant is culpable. This difference is why a prosecutor may lose in criminal court, but a civil plaintiff may win a claim relating to the same event. 

Elements of a Crime

To win a criminal case, the prosecutor must prove beyond a reasonable doubt that each element of a crime has occurred: 

  • The defendant took an action 
  • The defendant had intended to take that action
  • There’s concurrence—a connection in time—between the intent and action 

In some, but not all, cases, the prosecutor may also have to prove causation—that the defendant’s action resulted in some harm.

Actus Res (Action Taken)

To be proven guilty, a defendant voluntarily needs to take an action (also known as “actus reus”) that leads to the commission of a crime. But the defendant does not need to have completed every action required to commit the crime. For example, if someone died after drinking a poisoned smoothie, the prosecutor doesn’t have to prove that the defendant force-fed the smoothie to the victim—only that they poisoned the drink. 

Accomplice cases are an interesting example of an actus reus. For example, a bank robber is injured during a robbery. The bank robber’s friend hides the robber and treats his injuries until the robber can escape. Though there is no evidence the friend was directly involved in the robbery, by hiding the robber, he took an action that helped the robber commit the theft. Therefore, he’s just as culpable as the man who robbed the bank. The friend could be charged with aiding and abetting the robber, and—if convicted—the friend could receive the same punishment that the robber received. 

Conspiracy cases often offer another interesting example of an action taken. In conspiracy cases, all that may be required for a conspiracy conviction is an action taken in furtherance of the conspiracy. They don’t have to complete the crime they’d conspired about to be convicted of conspiracy.

Mens Rea (Intent)

To get a conviction, a prosecutor must also prove that the defendant had the requisite intent (a.k.a. mens rea) to take the abovementioned action. 

So if there was no intent, such as in the case of mistakes or accidents, there’s no crime. If someone in a parking lot drove off in another person’s car, genuinely believing it was their own because they’re identical, that’s not car theft.

What matters is if the robber took the act voluntarily and intentionally. 

TV shows and movies often spend a lot of time searching for a criminal’s motive, but the motive—why someone took an action—is unnecessary. That robber could have decided to commit the theft because he wanted to be rich or donate it to a charity. Motivation might help us identify a criminal, but it’s not relevant for determining their guilt. 

Laws state if a crime requires “specific intent” or “general intent.” A specific intent crime is when a statute outlines that the wrongdoer acts, intending a particular type of outcome to occur. A general intent crime addresses when a defendant commits a wrongful act but doesn’t necessarily intend the particular outcome. 

Laws also will set out levels of intent in terms of one’s state of mind—if they took an act 

  • purposefully
  • knowingly
  • recklessly or
  • negligently 

Purposefully and knowingly describe the degree to which someone affirmatively took an act that they knew would result in harm, while recklessly and negligently relate to when someone acts without caring about the outcome. 

Malice aforethought is another category that only relates to murder. It describes someone’s specific intent to kill. 

Examples of Act and Intent 

While these elements seem clear enough in theory, things get more complicated in application. 

Consider a law intending to address drunk driving. A specific intent law would state that a bartender breaks the law if they choose to continue serving a customer alcohol, knowing the customer was intoxicated and would drive drunk after leaving the bar. Because the bartender would make a conscious decision that leads to a specific result.

A general intent law could be that if an intoxicated driver is involved in a fatal accident, the prosecutor only needs to establish that the driver chose to drive drunk. It’s unnecessary to prove the driver intended to cause a fatal accident.   

“Felony murder” is a complex example of actus reus and mens rea. 

In a felony murder case, if a perpetrator commits a crime and a third party is killed during the commission of that crime, the perpetrator can be charged with felony murder—even when they had no direct involvement in the murder. Say, for instance, one person serves as the driver for a gang of thieves. The driver takes them to a jewelry store to rob the place. The driver never gets out of the car and is unaware of what is happening in the store. At one point, a thief shoots and kills a security guard. 

The driver can be charged with felony murder for the guard’s death. The driver had the general intent to participate in a felony, and he took the act of driving his partners so they could rob the store. Therefore, a felony-murder law provides that he can be held responsible for any death that happened during the commission of that crime. 

On the other hand, during the sentencing phase of the trial, the prosecutor would have to prove specific intent—that the driver intended for someone to die during the theft—if they’re asking for a death sentence. 

Concurrence / Causation

When it comes to concurrence, the prosecutor must prove if there’s a reasonable connection in time between the act and the intent. The events need to be close enough in time that there’s some nexus between the two. 

However, there’s some debate as to whether we should even include causation as an element of crimes. As we said, some intent laws require causation—the wrongdoer planned and caused a specific result—while others do not. 

And someone can be arrested for counterfeiting dollar bills before anyone has accepted the phonies.

This is in stark contrast to civil cases where the plaintiff proves how a defendant’s actions caused them harm and resulting damages. Without those, the plaintiff couldn’t get compensation.    

Defenses to a Criminal Charge

As we said at the beginning, a defendant doesn’t have to prove themselves innocent, but they may be able to defeat a criminal charge if they can provide convincing evidence that they didn’t do the act or they didn’t have the requisite intent (i.e., it was a mistake or accident). 

But there are also other defenses available for defendants to use: 

  • the act was taken in self-defense
  • the act was in defense of others
  • necessity (someone broke into a car to save an overheating child)
  • consent (you didn’t take the car because you rented it)
  • the law allows the conduct (police can knock out a violent suspect) 

“Not guilty by reason of insanity” is also a real defense, but it’s probably more likely to be seen on television than in a real courtroom.  

Understanding Sanctions/Punishment

When convicted of a crime, a defendant faces sanctions by the state, but these can vary depending on the crime’s type and severity.  

Two competing principles, punishment versus rehabilitation, drive how sanctions are meted out. Laws with strong prison sentences or other penalties aim to remove offenders from society and deter others from criminal conduct. 

On the other hand, the rise of drug-related diversionary programs is an example of prioritizing offenders’ rehabilitation rather than punishment.


As you’ve learned, even basic premises of criminal law can quickly become intricate and complex.That’s why you should have a great lawyer at your side—whether you are a potential defendant or a victim. To make sure that your interests are safeguarded, and that you put on the best possible case.  

Colin Bell is a DUI and Criminal Defense attorney in Phoenix, Arizona. He is Of-Counsel with Stewart Law Group with offices throughout Arizona. The firm has helped many clients navigate the legal complexities of DUI and criminal defense.  

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