Definition
Testable carries two distinct legal meanings that rarely intersect:
1. (Of a person) Having legal capacity to make a will. A testable person possesses both the age required by law and the mental competency — commonly called testamentary capacity — necessary for a valid testamentary act. The opposite of testable in this sense is intestable: a person legally incapable of making a will.
2. (Of property or an interest) Capable of being transferred by will; properly the subject of a testamentary disposition. Not all property interests pass by will; some are extinguished at death, some pass by operation of law, and some are held in forms that defeat testamentary transfer. Property that can be devised or bequeathed is testable in this narrower sense.
A third usage, distinct from wills law entirely, appears in evidence and procedure: in the Daubert framework governing expert testimony, testability refers to whether a scientific theory or methodology can be — and has been — subjected to empirical testing and potential falsification. This is a term of art drawn from philosophy of science, not from the law of wills, but it is firmly embedded in federal and state evidence doctrine governing admissibility of expert opinions.
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Common Language
Modern common usage (Wiktionary): Susceptible to being tested. In scientific usage, capable of being proven true or false through empirical methods.
Historical common usage (Webster's 1913): (1) Capable of being tested or proved. (2) Capable of being devised or given by will.
The legal meaning rooted in wills law — capacity to make a will — has no counterpart in ordinary modern English. Lay readers encountering "testable" will almost certainly import the scientific or everyday sense (capable of being tested), which is unrelated to testamentary capacity. The Daubert usage tracks the ordinary scientific meaning closely and will feel intuitive to modern readers, but it is a controlled term of art in evidence law, not a casual borrowing.
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Common Confusion
The two legal senses are easily conflated in cross-disciplinary research. A researcher working on testamentary capacity cases should not assume that "testable" in an evidence opinion means anything about wills, and vice versa. The Daubert sense of testable is methodologically precise — it asks whether a scientific proposition is falsifiable and whether testing has actually occurred — while the wills-law sense asks whether a human being or a property interest satisfies legal prerequisites for testamentary action. The words share a root but operate in entirely separate doctrinal worlds.
Testable (wills law) should also be distinguished from testate, which describes the condition of having died leaving a valid will, and from testamentary, which describes anything pertaining to or derived from a will.
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Recognized Forms
/SUBTYPES
Under the wills-law meaning, the concept subdivides by subject:
Testable person: One who has testamentary capacity — generally, majority age and sound mind as defined by the governing jurisdiction.
Testable property/interest: An asset or right that the law permits to pass by will, as opposed to interests that lapse, revert, or pass outside of the estate.
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Why It Matters in Research
Researchers face a bifurcated term. Historical legal sources — treatises, digests, and cases from the eighteenth through early twentieth centuries — use testable almost exclusively in the wills-law sense. When searching older corpus materials for testable, results will skew heavily toward testamentary capacity doctrine. The Daubert-era usage is a modern development; searching pre-1993 materials for testable in a scientific-reliability context will return few meaningful results and may surface false positives in wills disputes.
In the wills corpus, note that the historical sources set the age threshold at twenty-one years. This reflects the common-law age of majority. Most American jurisdictions have since reduced the age for testamentary capacity to eighteen, and military or married-minor exceptions exist in some states. Historical sources citing age twenty-one as the testable threshold should not be read as current law without verification.
Anderson's is the most useful of the historical dictionaries for this term: it supplies the second meaning (capable of being given by will, as property), cites actual authority, and flags the antonym intestable. Black's first and second editions reproduce near-identical entries focused on persons, not property, and omit the property-disposition sense entirely — a gap that can mislead researchers who stop at Black's.
The Rapalje & Lawrence entry contains an internal artifact: the entry for testable appears to carry over text (likely from testamentum or a neighboring entry) discussing conflicting clauses in wills and the maxim testamenta latissimam interpretationem habere debent. This spliced content is an editorial error in the source, not part of the definition of testable. Researchers relying on Rapalje & Lawrence for this term should treat only the opening clause — capacity to make a will — as the definition.
For Daubert research, the testability factor is one of four non-exclusive guideposts the Supreme Court identified for assessing expert methodology. It is not a checklist item that independently controls admissibility; courts weigh it alongside peer review, error rate, and general acceptance. Corpus materials on Daubert will index testability under evidence law, not wills law.
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Historical Dictionary Support
All four historical sources agree on the core personal sense: a testable person has capacity to make a will, possessing majority age and sound mind. This consensus is unremarkable — the term was not contested doctrine.
Anderson's adds substantive value by extending the definition to property (capable of being given by will) and by citing Depue v. Place, a Pennsylvania case, and secondary authority in Blackstone's Commentaries. It also cross-references intestable, giving the definitional pair that frames the concept. Anderson's is the richest entry in the set.
Black's first and second editions are identical to one another and thinner than Anderson's. They define the testable person but ignore testable property and the intestable antonym.
Rapalje & Lawrence open correctly but the entry is corrupted by interpolated text from an adjacent entry, rendering it unreliable as a standalone source for this term. The maxim about broad interpretation of wills is genuine and important in testamentary construction doctrine, but it belongs to a different entry.
None of the historical dictionaries address the scientific-falsifiability sense of testable, which postdates all of them. Researchers should not expect historical legal dictionaries to be useful anchors for Daubert analysis.
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Jurisdictional Note
The age threshold for testamentary capacity varies. Common law fixed it at twenty-one; most American jurisdictions now use eighteen. Some states permit married individuals or members of the armed forces to execute wills at younger ages. Historical sources uniformly citing twenty-one should be checked against current governing statutes before reliance.
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Encyclopedia Cross-Reference
Daubert Factors (Testability, Peer Review, Error Rate, General Acceptance) — Law Mind Civil Procedure & Evidence Encyclopedia
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