A veteran Johnstown High School teacher, whose teaching credentials have been brought into question, is now the object of a criminal investigation. The state attorney general's office is investigating whether Greater Johnstown social studies teacher and varsity basketball coach Dan Shipman falsified his credentials by using the test results of a friend. In previous cases, teachers who have falsified their certification have been charged with forgery or tampering with public records, which can be felony offenses. Officials from the state department of education say they have no record of Shipman's certification though Johnstown School officials say they did receive a copy of his certificate. Shipman has worked at Johnstown High School full time for six years.