Must an inventor "possess" an invention to patent it?

The requirements for patenting inventions relating to biotechnology have become increasingly strict and complicated in recent years. Despite early patent rulings that there is no need for an inventor to "reduce to practice" an invention, the courts are now ruling that an inventor must "possess" his or her invention before filing for patent. This review discusses what such "possession" may mean and describes decisions in which courts have found that an inventor has met or failed the possession test before filing for patent protection.