omission | Definition

Doc's CJ Glossary by Adam J. McKee
Course: Introduction / Criminal Law

An omission is a failure to perform legally required activities, a type of actus reus in criminal law.

What Is an Omission?

Firstly, an omission happens when an individual fails to perform an action that they’re legally obligated to do. It could involve anything from neglecting to pay taxes to failing to provide care for children. After all, both these activities are required by law.

Actus Reus and Omission

Furthermore, an omission is not just any failure to act. It falls under the umbrella of “actus reus” in criminal law. This term, “actus reus,” refers to the actual action or conduct that breaks a law. To put it differently, it’s the physical deed or wrongful behavior in a criminal offense. An omission, then, is considered a type of actus reus because it involves a form of wrongful behavior—specifically, the failure to carry out a legal duty.

Examples of Omission

For example, a parent who fails to feed their child commits an act of omission. The parent has a legal obligation to provide for the child’s needs, and by failing to do so, they are committing a criminal act. Not only is the parent failing to do what they should, but also their actions can cause harm to the child.

Similarly, if a person sees someone in immediate danger and does nothing to help, they may be guilty of an omission. In some regions, laws require people to assist others in immediate danger if they can do so without risk to themselves.

Why Omissions Matter in Criminal Law

Above all, omissions matter in criminal law because they can cause real harm, just like active crimes can. When a person neglects their legal duties, it can have serious consequences for others. Therefore, such neglect is not tolerated by the law. All in all, an omission is not a passive act but an active failure to fulfill a legal responsibility.

Omissions According to the Model Penal Code

The Model Penal Code (MPC) is a guideline used to help shape criminal law legislation in the United States. When it comes to omissions, the MPC has some specific views. Essentially, it outlines when a failure to act can lead to criminal liability.

Legal Duties and Liability

Under the MPC, an individual can only be held criminally liable for an omission if they have a legal duty to act. This legal duty can arise from several sources. For example, it could come from a statute that specifically states the person has a duty to act. Additionally, it could be due to a contract or the status of the relationship between the individuals involved. If such a duty exists and the person fails to fulfill it, then they may be held accountable for the results of their inaction.

The “Good Samaritan” Rule and Omissions

Interestingly, the MPC does not adopt what’s known as the “Good Samaritan” rule. This rule, present in some jurisdictions, places a legal obligation on people to help others in immediate danger if they can do so safely. The MPC, however, doesn’t include this as a general requirement. Therefore, under the MPC, a person who doesn’t assist someone in danger isn’t necessarily committing an omission unless there’s another legal duty compelling them to act.

Liable for Omissions: An Example

Let’s look at an example to illustrate how the MPC treats omissions. Suppose a parent leaves their child in a car on a hot day. The parent has a legal duty to care for their child and protect them from harm. By leaving the child in a dangerous situation, the parent has failed to perform that duty. Therefore, under the MPC, the parent could be held criminally liable for this omission.

The MPC outlines specific circumstances where an omission—or failure to act—can lead to criminal charges. It centers around the existence of a legal duty to act and emphasizes that not all failures to act are considered criminal omissions. It’s this nuance that differentiates the MPC’s treatment of omissions from other criminal law frameworks.


To sum up, an omission in criminal law refers to a failure to perform a legally required action. Whether it’s failing to pay taxes, neglecting to provide care for children, or not offering help when someone is in danger, omissions are considered serious crimes. They are a type of actus reus or guilty act, demonstrating that a crime doesn’t have to be a physical act—it can also be a failure to act.

Understanding this helps us grasp that all individuals have responsibilities under the law. We all must fulfill our legal obligations. Otherwise, we may face consequences in the criminal justice system. Remember, an omission can be just as harmful as an active crime.

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Last Modified: 07/11/2023

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