The statute of limitations for bringing legal action on a contract case is 6 years in MA and so you have a short amount of time to sue if that is what you wish to do. However, the remedy for failing to deposit a security deposit into an escrow account is to return the security deposit to the tenant and since the security deposit was technically returned to you in 2009 when you agreed to use it for rent, you have nothing to demand from the court.
See, e.g. Castenholz v. Caira:
"The relevant portions of subsection (3) (a) state that "[a]ny security deposit received by the [the landlord] shall be held in a separate, interest-bearing account in a bank . . . . A receipt shall be given to the tenant within thirty days after such deposit is received by the [landlord] which receipt shall indicate . . . the bank . . . the amount and account number of said deposit. Failure to comply with this paragraph [i.e., par. (a)] shall entitle the tenant to immediate return of the security deposit." Subsection (3) (a) thus imposes two duties on the landlord: first, to establish the escrow account, and, second, to furnish the tenant with a conforming receipt, both within a thirty-day period measured from receipt of the security deposit. Failure to conform with either duty represents a failure to comply with the paragraph and thus entitles the tenant to "immediate return of the security deposit." "
Now, if the security deposit had not yet been returned to you, then you would have the right to sue for the interest and treble damages and attorney's fees under the MA statute.
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