A patent holder in Canada has the exclusive right, privilege and liberty to making, constructing, using and selling the invention for the term of the patent, from the time the patent is granted. Any person who does any of these acts in relation to an invention without permission of the patent owner is liable for patent infringement. When faced with an action for patent infringement, the defendant has a number of defences that they can use. These roughly fall into three categories: Non-infringement, asserting that the defendant does not make, use or sell the patented invention; Invalidity, asserting that the patent should not have been granted in view of prior art; Defences based on user rights, statutory or otherwise. Remedies in Canadian patent law generally track both common law and equitable remedies. Equitable remedies include injunctions (both final and interlocutory) and an accounting of profits. Common law remedies include damages aimed at putting the plaintiff in the position he would have occupied had the infringement not occurred. Invalidity defences In order to obtain a patent, an invention must be: Allowable subject matter; New; Useful; Not obvious to a person skilled in the art. The Canadian Patent Act allows that: Therefore, if a person can show that a patent claims improper subject matter, is anticipated, inoperable or obvious, then the patent can be declared void. For example, if a defendant can show evidence that the claimed invention was known as of the claim date, and thus the invention is not new, the patent can be declared void. Improper subject matter Under section 2 of the Patent Act, an invention is defined as: If the defendant can successfully show that the invention does not fall into any of these classes, then the patent will be invalid. There are a few cases where this has occurred, such as Harvard College v. Canada (Commissioner of Patents). In that case, it was held that while the genetically engineered plasmid and transgenic mouse cells were the proper subject of a patent, the genetically modified mouse and other higher life forms were not. Lack of utility or inoperability In applying for a patent, the applicant must show that the patent is operable as of the claim date. The claim itself must specify the invention in enough detail that a person skilled in the art would be able to reproduce the invention. In lieu of an operable invention,