An interested witness is a person who gives evidence or attests a document while having a personal stake in the matter, such as a financial benefit or relationship to a party. In wills and probate practice, it commonly means an attesting witness who is also a beneficiary, or is married to (or, in some jurisdictions, the civil partner of) a beneficiary. In England and Wales, section 15 of the Wills Act 1837 renders void any devise, legacy or other testamentary gift in favour of an attesting witness or their spouse or civil partner, but the will and the attestation remain valid and the witness is competent. Northern Ireland has a substantially similar rule in its wills legislation. In Ireland, section 82 of the Succession Act 1965 likewise voids the gift to the attesting witness (and to their spouse) without invalidating the will. In Scotland, a beneficiary may witness a will; the Requirements of Writing (Scotland) Act 1995 imposes no forfeiture, though any interest may affect evidential weight. Outside probate, interested witness is a descriptive evidential label used across civil and criminal proceedings: testimony from a party, associate or accomplice is admissible, but may attract cautionary treatment on credibility and weight.