Aronstein v. Mass. Mutual Life Ins. Co., 15 F.4th 527

Background

MassMutual reduced the Odyssey annuity's minimum guaranteed interest rate from 3.0% to 1.5% in 2003 by attaching a one‑page "GUARANTEED INTEREST RATE ENDORSEMENT" to the certificate rather than rewriting the certificate.
The certificate prominently listed a 3.0% "Minimum Guaranteed Interest Rate," included payout schedules based on 3.0%, and did not reference 1.5%; the single endorsement page was not listed in the table of contents and was sandwiched between the certificate and the application.
Purchaser Jesse Aronstein was told by a sales agent (and given marketing materials) that the annuity guaranteed 3.0%; he signed the papers but did not notice the endorsement until years later when statements showed credited interest below 3.0%.
Aronstein sued for breach of contract (and brought a class claim); the district court held the contract ambiguous, denied class certification (common issues did not predominate), tried Aronstein’s individual claim and entered judgment for him with prejudgment interest.
On appeal, Aronstein challenged denial of class certification; MassMutual cross‑appealed the judgment and conditionally cross‑appealed the prejudgment interest award; the First Circuit affirmed the judgment for Aronstein, affirmed denial of class certification, and awarded costs to Aronstein.

Issues

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the contract unambiguously fixed the minimum guaranteed rate at 1.5%	Aronstein: reasonable reading of the certificate supports a 3.0% guarantee	MassMutual: the endorsement unambiguously controls and sets rate at 1.5%	The contract was ambiguous as to the minimum guaranteed rate; ambiguity required factfinding and was construed against MassMutual after extrinsic evidence failed to resolve it
Whether extrinsic evidence is admissible or whether doctrines would bar it (e.g., intentional ambiguity / standardized‑form uniform interpretation)	Aronstein: New York would adopt doctrines making extrinsic evidence irrelevant, enabling classwide relief	MassMutual: New York law requires consideration of extrinsic evidence and uses contra proferentem only as a last resort	Court declined to expand New York law; extrinsic evidence is considered first and contra proferentem is a last resort
Class certification — whether common issues predominate under Rule 23(b)(3)	Aronstein: classwide issues can resolve the dispute	MassMutual: individual inquiries into what each purchaser believed and what sales agents told them will predominate	Denial of class certification affirmed because individual extrinsic‑evidence inquiries would predominate
Prejudgment interest — whether award should be disturbed	(n/a on appeal after conditional cross‑appeal)	MassMutual conditionally cross‑appealed but agreed to drop challenge if certain rulings affirmed	MassMutual waived its challenge to prejudgment interest by conditionally abandoning it once the denial of class certification was affirmed

Key Cases Cited

Westmoreland Coal Co. v. Entech, 794 N.E.2d 667 (N.Y. 2003) (contracts read as a harmonious, integrated whole)
County of Columbia v. Cont'l Ins. Co., 634 N.E.2d 618 (N.Y. 1994) (endorsement and policy read together; policy terms remain except as altered by endorsement)
Universal Am. Corp. v. Nat'l Union Fire Ins. Co. of Pittsburgh, Pa., 37 N.E.3d 78 (N.Y. 2015) (ambiguity exists when terms permit more than one reasonable interpretation)
Kowalczyk v. Flintkote Co., 405 N.Y.S.2d 852 (N.Y. App. Div. 1978) (conflict between a header and text may create ambiguity)
Carlson v. Am. Int'l Grp., Inc., 89 N.E.3d 490 (N.Y. 2017) (extrinsic evidence examined before applying doctrinal presumptions like contra proferentem)
Fairchild v. Genesee Patrons Coop. Ins. Co., 656 N.Y.S.2d 544 (N.Y. App. Div. 1997) (if extrinsic evidence does not resolve ambiguity, interpret against insurer)
In re Nexium Antitrust Litig., 777 F.3d 9 (1st Cir. 2015) (standard of review for class certification decisions)
Calandro v. Sedgwick Claims Mgmt. Servs., Inc., 919 F.3d 26 (1st Cir. 2019) (bench‑trial findings reviewed for clear error; legal conclusions de novo)
Erie R.R. Co. v. Tompkins, 304 U.S. 64 (1938) (federal courts in diversity apply state substantive law)