Trespass to chattels vs. conversion: civil claims over someone else’s property

Trespass to chattels and conversion are civil claims for interfering with another person’s personal property. Trespass to chattels covers lesser interference, such as damaging an item or keeping the owner from using it for a while, and pays for the actual harm. Conversion covers interference so serious that the wrongdoer must pay the item’s full value. California’s jury instructions describe trespass to chattels as surviving “largely as a little brother of conversion” (CACI No. 2101).

What a chattel is

A chattel is movable property. Cornell’s Wex encyclopedia says that in modern usage the word “usually only refers to tangible movable personal property,” such as a phone, a car or a tool (Wex: chattel). Land and buildings are real property, and Wex notes that conversion does not apply to them (Wex: conversion). Wex is an educational, secondary source, not a statute or court ruling.

Trespass to chattels: elements and damages

Wex describes trespass to chattels as intentional interference with “the possession or use of personal property” belonging to someone else, resulting in harm (Wex: trespass to chattels). In California, the official jury instruction lists five things the person bringing the claim must prove:

• they owned, possessed or had a right to possess the item;
• the defendant intentionally interfered with their use or possession of it, or damaged it;
• they did not consent;
• they were harmed; and
• the defendant’s conduct was a substantial factor in causing the harm.

Harm matters. The California instruction quotes case law saying the owner “may recover only the actual damages suffered by reason of the impairment of the property or the loss of its use.” In other words, the award tracks repair costs or the value of lost use, not the price of a replacement.

Conversion: elements and damages

Under California’s CACI No. 2100, a conversion claim also requires ownership or a right to possess, lack of consent, harm and causation. The difference is in the second element: the defendant must have “substantially interfered” with the property by knowingly or intentionally taking it, blocking access to it, destroying it, or refusing to return it after the owner demanded it back (CACI No. 2100).

The intent needed is narrow. California case law quoted in CACI says conversion “must be knowingly or intentionally done, but a wrongful intent is not necessary,” and that mistake and good faith are ordinarily not defenses. Carelessness alone is not conversion. Wex gives a similar example: someone who picks up a necklace believing it was abandoned, intending to resell it, still converted it.

In California, the damages rule is set by statute. Civil Code section 3336 presumes the loss is “the value of the property at the time of the conversion, with the interest from that time,” or an amount covering the natural and reasonable losses the wrongful act caused, plus “fair compensation for the time and money properly expended in pursuit of the property” (Cal. Civ. Code § 3336). The matching jury instruction, CACI No. 2102, defines fair market value as the highest price a willing buyer would pay a willing seller, with neither under pressure. Other states measure damages under their own rules.

How courts tell the two apart

The line is one of degree. A California appellate court, quoted in the notes to CACI No. 2101, explains that trespass to chattels covers interferences “not sufficiently important to be classed as conversion, and so to compel the defendant to pay the full value of the thing with which he has interfered” (CACI No. 2101). A conversion judgment makes the defendant buy the property, so courts reserve it for serious interference.

Massachusetts’ model jury instruction, citing Restatement section 222A(2), asks jurors to weigh these questions (Massachusetts model instruction):

• how much control the defendant exercised, and for how long;
• whether the defendant intended to make a claim that conflicted with the owner’s right of control;
• whether the defendant acted honestly;
• how much the defendant interfered with the owner’s control, and for how long;
• how much expense and inconvenience the owner suffered.

The harm done to the property also matters. A classic illustration, quoted in California’s CACI No. 2101: taking someone’s hat by mistake and returning it within two minutes is not conversion, though trespass may still apply.

Can money be converted?

Sometimes. In California, case law quoted in CACI No. 2100 says money “cannot be the subject of a cause of action for conversion unless there is a specific, identifiable sum involved,” such as an agent who accepts a payment for someone else and fails to pass it on. A general claim that someone owes you money is usually a contract or debt claim instead. The California Supreme Court, also quoted there, said a claim for unpaid wages has long been understood to “sound in contract, rather than as the tort of conversion.” Massachusetts takes a similar view, requiring a right to specific funds and not just a debt (Massachusetts model instruction).

How this differs from criminal theft

Conversion and theft can involve the same act, but they are different proceedings. Wex explains that crimes are wrongs against the state or society, while torts are private wrongs aimed at compensating the victim (Wex: tort). The government prosecutes theft. The owner brings a conversion claim.

The mental state differs too. California’s theft statute covers a person who shall “feloniously steal” property or “fraudulently appropriate property” entrusted to them (Cal. Penal Code § 484). Conversion, by contrast, can apply to an honest mistake. Someone may face a civil claim without ever committing a crime.

Questions to sort a property dispute

• Did you own or have a right to possess the item? Both torts start there.
• What exactly happened to it? Damaged, used, kept, sold or destroyed.
• For how long? Brief interference points toward trespass; long or permanent loss points toward conversion.
• Did you ask for it back? Keep a record of any demand and the response.
• Which state’s law applies? Elements and damages rules differ; a lawyer licensed in that state can tell you how they apply.

This guide explains general legal concepts and is legal information, not legal advice. Rules for trespass to chattels, conversion and theft differ by state and depend on the facts; consult a lawyer licensed in the relevant jurisdiction about a specific situation.