The lawyer for the latest person of interest in the investigation into the mysterious 1990 art heist at Boston’s Isabella Stewart Gardner Museum said today that his client, despite being hounded by investigators for at least two years, maintains he has no information about the notorious crime. A. Ryan McGuigan, the lawyer for 75-year-old Robert Gentile, said federal prosecutors are torturing his client by keeping him jailed on drug distribution charges in Connecticut in an effort to squeeze information out from him about the museum heist.