It is legal and it is also likely, especially if the amount of the claim is a significant amount. As long as the investigator is not infringing on your privacy, then it is legal. In order to avoid any issues that could jeopardize your claim, it is important to always be honest about your injury. Do not exaggerate the extent of injuries, but also do not push yourself to do things your body is not physically ready to do, such as go back to work too soon or work on household chores.