You freeze when you see it on the MBE. A convoluted fact pattern about someone’s unborn grandchildren inheriting property. Language about “when” and “if” scattered everywhere. You know it’s testing the Rule Against Perpetuities, and you know that means trouble.

Here’s the truth: RAP questions feel deliberately designed to break your brain. But the rule itself isn’t actually that complicated once you strip away the archaic language and focus on what the examiners are really testing. You don’t need to become a medieval property scholar. You need a systematic approach that works under pressure.

What the Rule Against Perpetuities Actually Says

The Rule Against Perpetuities (RAP) is a common law rule that invalidates certain future interests if they might vest too far in the future. Here’s the classic formulation you’ll see everywhere:

No interest is valid unless it must vest or fail within a life in being at the creation of the interest plus 21 years.

Read that again slowly. The rule doesn’t say the interest will vest within that time period. It says it must vest or fail. If there’s any possible scenario—no matter how absurd—where the interest could vest outside the perpetuities period, the entire interest is void from the start.

That’s the trap. The MBE tests whether you can spot these remote possibilities, not whether they’re likely to happen.

When Does RAP Apply?

Before you panic about vesting, make sure RAP even applies to the interest in question.

RAP applies to three types of future interests:

RAP does NOT apply to:

Why the distinction? The interests exempt from RAP are either already vested or retained by the grantor. The rule targets future interests that create uncertainty too far into the future.

If the MBE gives you “to A for life, then to B,” you’re done. That’s a vested remainder in B. No RAP analysis needed. Move on.

The Perpetuities Period: Lives in Being Plus 21 Years

The measuring period starts when the interest is created—at the time of the conveyance for inter vivos transfers, or at the testator’s death for wills.

A life in being means someone who is alive when the interest is created. It doesn’t have to be the grantee or even someone mentioned in the conveyance. You’re looking for any life that can be used to prove the interest must vest or fail within the required time.

Here’s a straightforward example: “To A for life, then to A’s children who reach age 25.”

Is this valid? A is your life in being. When A dies, we’ll know exactly who A’s children are. The oldest child might not reach 25 for another 25 years, which exceeds 21 years after A’s death. This violates RAP. The contingent remainder to A’s children is void.

Now tweak it: “To A for life, then to A’s children who reach age 21.”

Valid. When A dies, A’s children have at most 21 years to reach 21. The interest must vest or fail within a life in being (A) plus 21 years.

The Classic RAP Traps on the MBE

The examiners love certain hypothetical scenarios that violate common sense but follow RAP logic. You need to recognize these patterns instantly.

The Fertile Octogenarian

Under RAP, every person is presumed capable of having children regardless of age or medical reality. Yes, even an 80-year-old woman.

Example: “To A for life, then to A’s children who graduate from law school.”

A is 85 years old with two adult children. Seems safe, right? Wrong. A is conclusively presumed capable of having more children. If A had another child tomorrow who didn’t graduate law school until 50 years from now, the interest would vest too remotely. The entire gift to A’s children fails.

The Unborn Widow

A reference to someone’s “widow” or “widower” might refer to someone not yet born when the interest is created.

Example: “To A for life, then to A’s widow for life, then to A’s surviving children.”

Even if A is currently married, A could divorce, remarry someone born after the conveyance, and that new spouse could outlive A by more than 21 years. The remainder to A’s surviving children might not vest until the widow dies—potentially beyond the perpetuities period. Void.

The Slothful Executor

Conditions tied to the completion of probate or estate administration can violate RAP because these processes might take longer than 21 years.

Example: “To A when my estate is fully administered.”

There’s no life in being to measure against. Estate administration could theoretically drag on for decades. The springing executory interest to A is void.

Class Gifts: All or Nothing

Here’s where students lose points. With class gifts, if any member’s interest might vest too remotely, the entire class gift fails. You can’t save the valid members and void the rest.

Example: “To A for life, then to A’s grandchildren who reach age 25.”

When A dies, A might have grandchildren under age 4. Those grandchildren wouldn’t reach 25 until more than 21 years after A’s death. Even though some grandchildren might already be over 25 when A dies, the whole class gift is void because we measure validity at the time the interest is created, not when it vests.

How to Analyze RAP Questions Systematically

Stop trying to memorize outcomes. Use this process every single time:

Step 1: Identify the future interest. Is it contingent, executory, or a class gift subject to open? If not, RAP doesn’t apply.

Step 2: Find the condition that must occur for the interest to vest. What has to happen?

Step 3: Ask: Is there any possible scenario where that condition might occur more than 21 years after everyone currently alive has died?

Step 4: If yes, the interest is void. If no, it’s valid.

Let’s apply this to a typical MBE hypothetical:

“O conveys Blackacre to A for life, then to B if B reaches age 30. B is currently 20 years old.”

Step 1: B has a contingent remainder (condition precedent: reaching age 30).

Step 2: The condition is B reaching 30.

Step 3: B is a life in being. B will either reach 30 during B’s own lifetime or die before reaching 30. Either way, the condition will be satisfied or fail within B’s lifetime—which is definitely within a life in being.

Step 4: Valid.

Now change it: “O conveys Blackacre to A for life, then to the first child of A to reach age 30.”

Step 1: Contingent remainder in A’s child.

Step 2: A’s child reaching age 30.

Step 3: A could have a child born after the conveyance. That child wouldn’t reach 30 until 30 years after birth. If A died immediately after that child’s birth, the interest wouldn’t vest until 30 years after A’s death—9 years too late.

Step 4: Void.

Modern Reforms You Might See

Many jurisdictions have reformed or abolished RAP, but the MBE still tests the common law rule. However, you should recognize these modern approaches in case a question specifically invokes them:

Wait-and-see: Instead of voiding an interest based on what might happen, courts wait to see what actually happens. If the interest actually vests within the perpetuities period, it’s valid.

Uniform Statutory Rule Against Perpetuities (USRAP): Provides an alternative 90-year vesting period. An interest is valid if it either satisfies the common law rule or actually vests within 90 years.

Cy pres (judicial reformation): Courts modify the interest to comply with RAP rather than voiding it entirely, attempting to honor the grantor’s intent.

Unless the MBE question specifically tells you a jurisdiction has adopted one of these reforms, apply the common law rule.

What to Memorize for Test Day

Lock these points into your memory:

The FlashTables Real Property guide covers all of these RAP traps in a structured format alongside the 14 other future interest rules you need to distinguish on the MBE. When you’re drilling practice questions and spot a perpetuities issue, you want the rule elements and common exceptions immediately accessible—not buried in your outline somewhere between adverse possession and easements.

RAP questions aren’t testing your ability to predict the future. They’re testing whether you can mechanically apply an archaic rule to bizarre hypotheticals. Once you stop trying to make the scenarios realistic and start treating them like logic puzzles, these questions become far more manageable. You’ve got this.