Jeffries, Administrator v. Mutual Life Insurance Company of New York was a case heard by the United States Supreme Court in 1884. The case involved a dispute between the administrator of the estate of a deceased man and the insurance company that had issued a policy on the man's life. The administrator argued that the insurance company had failed to pay the full amount of the policy, and he sought to recover the difference. The insurance company argued that the policy had been forfeited due to the man's failure to pay the premiums. The Supreme Court held that the insurance company was not entitled to forfeit the policy due to the man's failure to pay the premiums. The Court reasoned that the policy was a contract between the parties, and that the insurance company had not provided any notice to the man that the policy would be forfeited if he failed to pay the premiums. The Court also noted that the insurance company had accepted the man's payments for the premiums, and that the company had not taken any action to terminate the policy. As a result, the Court held that the insurance company was liable to the administrator for the full amount of the policy.

In Jeffries, Administrator v. Mutual Life Insurance Company of New York, the Supreme Court was asked to decide whether a contract between two parties that had been modified by one party without the other's consent could be enforced in court. The majority opinion held that such contracts were not enforceable and thus dismissed the case. However, Justice Field dissented from this decision on the grounds that it would lead to injustice for those who had relied upon an agreement made in good faith but which was later changed unilaterally by another party without their knowledge or consent. He argued that if courts refused to recognize these agreements as valid then they would be encouraging people to break their promises and undermine public confidence in contractual obligations more generally. Furthermore, he noted that there were many cases where modifications of contracts are necessary due to unforeseen circumstances and should therefore still be recognized as legally binding even when only one party has agreed to them