What Is Substantive Defense?

Matt Pinsker

March 10, 2023

What Is Substantive Defense?

Substantive defense law is the body of law that governs all legal issues, including rights and obligations. It includes both civil and criminal laws.

Today, most substantive law is codified in federal and state criminal codes. It defines the elements of a crime, what defenses may be raise, and what penalties are require.

Mistake of law

A mistake of law is a defense that allows a defendant to challenge a criminal charge if they are unaware that the act they committed was illegal. However, this is only a defense in limited situations and usually only serves as a partial defense.

To use this defense, a defendant must be honest and reasonable. For example, a defendant may argue that they mistakenly thought they could steal a coat from a store when they were not allow to do so.

Another example of this is when someone is charge with statutory rape. If they are accuse of committing this crime, they often argue that they didn’t know their sexual partner was under 18 years old, a fact that violates the statute.


The justification for substantive defense is a defendant’s argument that an act was the right thing to do, even if it resulted in harm. This is a common defense when society recognizes that some acts are beneficial and should not be punish because of their consequences.

Substantive law is a legal concept that determines the rights and obligations of individuals. It may come from the common law, statutes, or a constitution.

Today, the vast majority of substantive law has been codified. Most of it is found in state or federal criminal codes.

Substantive laws include definitions of crime, which tell us what elements the government must prove to establish that a crime has been committed. It also includes definitions of inchoate crimes (incomplete crimes) involving conspiracies, solicitations, and attempts, as well as accomplice liability (when a person will be held responsible when they work in concert with others to complete a crime). Finally, it identifies the defenses that may be raise by the defendant and indicates the appropriate penalties and sentences for crimes.

Ineffective assistance of counsel

When an attorney fails to perform their duty to represent you, that conduct may qualify as ineffective assistance of counsel. The test for ineffective assistance of counsel requires that a defendant show (1) that the attorney’s performance fell below an objective standard of reasonableness; and (2) that, but for the deficient performance, the proceeding results would have been different.

The Supreme Court has held that a defendant’s Sixth Amendment right to counsel includes the right to effective legal representation at trial. However, proving ineffective assistance of counsel is a complex matter.

The Strickland test governs ineffective assistance of counsel claims involving guilty pleas; the appellant must demonstrate that his attorney was deficient and that there is a reasonable probability that, but for the errors, he would not have pled guilty or insisted on going to trial. Moreover, he must also show prejudice caused by the errors.

Defendant’s mental state

A defendant’s mental state is important because it can influence their decision to plead guilty or not guilty, and it can have a major impact on the outcome of a trial. If you are accuse of a crime and believe that your mental state played a role in the outcome, it is crucial to reach out to a qualified Massachusetts criminal defense lawyer as soon as possible.

In many states, a defendant can be acquitte of a crime by proving that they could not commit the offense because they were suffering from a mental illness or defect at the time of the offense. This defense is often use by people who have a mental illness that is severe enough to prevent them from understanding the consequences of their actions or from recognizing whether they have done something wrong.