The Medical certificate is not fake but fraudulently obtained with the conspiracy of hospital authorities for unlawful gains of harassing others. Entrust this to a Detective agency. If you are capable of investigating yourself, go through RTI way and seek certified copies of the Admission register, and other records that state that Mrs.Kakashi has been treated in that hospital. Visit the office and observe whether there is CCTV footage available on that date and contact insiders to know the lai down the process and the way you can expose the fraud. Always focus on the main issue alone and do not be distracted by threats or fights with others.