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You Got Latin in My English! Legal Terms, Part 2

It's time for another edition of "You Got Latin in My English!" This series focuses on Latin terms that are commonly used in English; I provide the literal meanings of the terms and then explain how to use them in context.

In this post—the second on this subtopic—I focus on seven more Latin legal terms. (Read Part 1 here.) The terms covered below are commonly used in legal cases but are not generally known outside that sphere; still, they are often used in coverage of legal cases and in proceedings that ordinary people are sometimes involved in.

After reading this post, you will be able to better understand and converse about these legal terms: amicus curiae, (non) compos mentis, corpus delicti, in loco parentis, lis pendens, mandamus, and pro se / pro per.

You Got Latin in My English! Legal Terms, Part 2: amicus curiae, (non) compos mentis, corpus delicti, in loco parentis, lis pendens, mandamus, and pro se/per

Amicus Curiae

Literal Translation: "friend of the court"

In U.S. law and various international courts*, the term amicus curiae has the same meaning that it did in Latin: "friend of the court." It can be used to refer to an expert in a subject matter related to a case or to an organization whose business is related to a case. Any individual, group, or organization can file what is known as an "amicus curiae brief"—a written statement providing key information or an informed opinion related to the case at hand. (In other jurisdictions, this type of brief is called an "intervenor.")

* In Canadian law, the term amicus curiae has a different meaning; it refers to a lawyer who is brought into court to provide arguments regarding an issue that otherwise would not be considered properly—usually because one party does not have a lawyer. This clearly also relates to the meaning "friend of the court."

The most common type of amicus curiae today is an advocacy group; by filing briefs, these groups seek to provide greater context on the ramifications of a case. For instance, the National Civil Liberties Union often files amicus curiae briefs on appellate and Supreme Court cases related to civil rights. The lawyers in these cases typically must focus on the legal issues, so the amicus curiae briefs serve to provide additional context for the judges involved.

In other cases, amicus curiae briefs come from historians or other subject-matter experts. These individuals provide the court with their expertise so as to affect the judges' decisions. Here are a couple examples of the term amicus curiae in action:

The National Rifle Association acted as an amicus curiae for the Supreme Court, submitting a brief in which it argued against all gun regulations. The judges were swayed by the statistician's amicus curiae brief, which provided data to support the plaintiff's case.

(Non) Compos Mentis

Literal Translation: "(not) of sound mind"

Compos mentis (and its opposite, non compos mentis) refer to whether a person is mentally able to make rational decisions for themselves (literally, whether they are "of sound mind"). A person who was non compos mentis when they performed an action is likely to be punished less severely for any consequences of that action than they would be if they were mentally sound. In addition, a judge will only allow a person to act as their own lawyer if that person is compos mentis.

This term originally was most commonly used to refer to supposed diabolical or supernatural influence (as when a person claimed that the devil made them do something). Over time, compos mentis has become more associated with insanity or mental illness. These terms can also be used outside of legal contexts, such as to refer to a person who is confused, intoxicated, or otherwise acting irrationally.

Here are a couple sentences with these terms:

The jury found that the defendant was compos mentis at the time of the crime and thus rejected the claim of temporary insanity. Mirabelle attempted to drive home, but because she was non compos mentis, she could not even successfully open her car door.

Corpus Delicti

Literal Translation: "body of the crime"

The term corpus delicti is used in Western countries to refer to a key principle: that a person cannot be accused of a crime unless that crime has been proven to have occurred. This term literally means "body of the crime," and it is best illustrated using an example: A person cannot be charged with murder unless authorities can prove that the victim was, in fact, killed. This is typically done by finding the "body of the crime" (usually the victim's remains) and then showing that the person's death was the result of an illegal action (i.e., that they were killed and did not die accidentally).

A lack of corpus delicti causes prosecutors to charge suspects for lesser (but more easily proven) crimes—or to not charge them at all. For instance, mobsters are rarely charged with murder, in part because the victims' bodies often cannot be recovered. However, it is much easier to prove that financial crimes, so authorities can often secure convictions of these individuals (e.g., Al Capone) for crimes such as money laundering and tax fraud.

Here is how you use corpus delicti in a sentence:

The judge dismissed the case because of a lack of corpus delicti, as there was no proof that the plaintiff's bicycle was even stolen—much less by the defendant. We established corpus delicti by proving that the victim died while being attacked.

In Loco Parentis

Literal Translation: "in place of a parent"

In law, children are typically considered the responsibility of their parents. However, in some cases, other individuals or organizations must act on behalf of children; this is called in loco parentis (literally, "in place of a parent"). This typically occurs in two scenarios: (a) when an organization (e.g., a school) is responsible for many children and (b) when someone other than a parent or legal guardian takes on those responsibilities for a child.

In the first case, in loco parentis is used to give an organization the ability to act in the best interests of the children in its care (but not to violate their civil rights). For instance, a primary or secondary school can set rules that are intended to protect their students. This is a complicated topic and the subject of much ongoing debate with regard to the extent of students' rights when at school. For instance, current rulings protect students' right to free expression in most cases but allow schools to restrict students from disrupting their classrooms as part of this expression (as this interferes with other students' education).

In the second case, in loco parentis refers to a person who essentially acts as a parent for a child. For instance, long-term babysitters have the ability to act on behalf of their charges. Here's some examples of this term in use:

Due to the rule of in loco parentis, private schools often have wide latitude to restrict their students' actions. After caring for her neighbor's son for most of the past 10 years, the court granted Pima the right to represent the boy's interests.

Lis Pendens

Literal Translation: "suit pending"

In U.S. law, a lis pendens (literally, "suit pending") is a written notice of a lawsuit filing; it is typically related to real-estate transactions. For instance, lis pendens notice establishes a plaintiff's claim on a property and alerts other parties (such as mortgage lenders) that the ownership of the property is in dispute. It is usually filed with the local organization that keeps track of land ownership (e.g., a county land records office).

Though this is a fairly technical term, it can come up in ordinary people's lives because anyone can purchase property. Here is an example of lis pendens in action:

Roger filed a lis pendens with the county to indicate that he was suing for control of the disputed property on Elm Lane.


Literal Translation: "We command."

Due to the multilevel nature of the U.S. government (and those of other countries), there are often conflicts between local or state courts or governments and their federal superiors. In such cases, an upper court can command a lower authority to act (or not act) in a certain way using a writ of mandamus (literally "we command").

A writ of mandamus must be based on a legal obligation, and it must be enforceable. It is intended to remedy a failure of justice. A person may ask for mandamus, for instance, when a state or local government restricts their federal constitutional right to freedom of religion (perhaps by passing a law banning clothing associated with a certain religion). The writ, if granted, would then require the lower government to stop restricting that right (in this case, by allowing the person to wear the clothing).

Here is an example:

The federal appeals court sent a writ of mandamus to the city of Pasadena, ordering it to stop restricting public protests.

Pro Se & Pro Per

Literal Translation: "for himself" & "for oneself"

Pro se and pro per are used interchangeably in legal settings to refer to the act of defending oneself in court. They literally mean "for himself" and "for oneself," and they are used as adverbial phrases. Here is how to use them in context:

Defendants in traffic court typically act pro per for minor offenses, which have quick and easy-to-follow trials. The judge tried to discourage Milena from acting pro se and recommended that she listen to her appointed lawyer.

That's all for this edition of You Got Latin in My English! I hope you enjoyed learning about the origins and meanings of these Latin legal terms.

Are there any other Latin terms that you would like me to explain in a future post in this series? If so, let me know in the comments or via email ( And of course, if you don't want to worry about the proper usage of these terms—or about making sure your writing is grammatical, clear, concise, and well-structured—then please request a quote or consultation at I'd love to help you improve your writing!



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