Mass. Gen. Laws ch. 236 § 34
The debtor may in all cases cause the amount due for redemption to be ascertained at his own expense by three justices of the peace in the manner following: one of the justices shall be chosen by the debtor, one by the creditor, and one by the two first chosen; or if the creditor neglects to choose one, the justice chosen by the debtor shall appoint the other two. After a hearing before the three justices, they or two of them shall make and sign a certificate of the amount which they adjudge to be due for the redemption of the land, which certificate shall be final and conclusive between the parties. A tender by the debtor of the amount so adjudged to be due shall be a sufficient tender notwithstanding any previous tender.
Mass. Gen. Laws ch. 236, § 34