Telling perspective employers that I threatened to kill my supervisor

Can a former employer tell a perspective employer that you made threats against other employees. I was terminated from a job after 5 years. I was given an exit interview at HR. Shortly after that I was called by a perspective employer and asked "did you really threaten to kill your supervisor"?. When I called HR to enquire as to why this was being said, and who was saying it, I found that the person that was saying this no longer works for the company. This was only 6 weeks after the interview. It has been over 7 months since my termination, and I still am having problems finding a job, not to mention still being asked if I threatened to kill my supervisor.
I currently am unemployed and cannot afford a consultation fee, although I will pay as much as I can.