If all the subscribing witnesses to the deed are also dead or out of the commonwealth, the due execution thereof may be proved before such court by proving the handwriting of the grantor and of a subscribing witness.
Mass. Gen. Laws ch. 183, § 35
Proof of execution by proving handwriting
Official source: Massachusetts Legislature. Reproduced from public-domain Massachusetts statutes; confirm against the official source for the current text. Not legal advice.