[1] Practicing law in New York at 342 Madison Avenue, McCoy started his legal career with Eaton, Lewis & Rowe before becoming an assistant United States Attorney in 1921.
[2][3] McCoy was "instrumental in breaking up the nation-wide blind pool," known as the participating syndicates in the "Ponzi System," when he prosecuted Leonard K. Hirshberg and members of the Winthrop Smith Company, leading to indictments.
[4][5] As an assistant United States Attorney General, McCoy was successful at prosecuting brokers for mail fraud.
[1] Among other cases, he successfully prosecuted Austin H. Montgomery Jr. and others, who were charged with using blind pools operated by the Community Finance Corporation to defraud $3,000,000 through mail fraud.
[6] Others indicted in the same case included John A. Berryman, for using the mails to defraud investors in connection with Fidelity Finance Company.
For selling securities in a similar operation to Community Finance Corporation, Berryman surrendered to Peter J. McCoy in August 1923.
[6] In September 1923, after being accused of a $6,000,000 blind pool deal concerning the Community Finance Corporation, Montgomery was found in Quebec, Canada.
Schwartz were put on trial on an indictment "charging fraudulent use of the mails in connection with the operation of a blind pool by the Community Finance Corporation."
[9] Eight people were indicted for mail fraud total on July 20, including Austin H. Montgomery Jr. of New York, by the Federal Grand Jury, after post office inspectors looked into the activities of Fidelity Finance Company.
[11] Working out of the Anti-Fraud Bureau on the issue, Albert Ottinger started an investigation into the failures in earnest in late May 1923.
[16] According to the New York Times, McCoy prosecuted many people who were accused of violating the Food and Drug Acts, selling narcotics, and counterfeiting.
[1] McCoy also prosecuted those indicted in the Crager System, or "glass casket case," for "fraudulently using the mails in the sale of stock of the concern.