Federal prosecutors announced the case closed on investment fraud schemes that took $23 million from 700 people across the country, targeting elderly and unsophisticated investors with pitches about backers like an ex-Apple Inc. CEO, they said.

U.S. District Judge Marcia G. Cooke in Miami sentenced Craig Sizer, 49, of Miami to 15 years in prison Wednesday after he pleaded guilty to conspiracy to commit wire and mail fraud, prosecutors announced.

Acting U.S. Attorney Benjamin Greenberg of the Southern District of Florida and FBI Special Agent in Charge George Piro of the Miami field office detailed the case in a joint announcement Friday. They said that from April 2009 to August 2015, Sizer and his co-conspirators, who have already pleaded guilty, used false and fraudulent claims to solicit investors all over the country to buy shares of stock in Sanomedics International Holdings, a company that sold noncontact infrared thermometers for home health care and for dogs.