Well it should be the victim or victim's family lobbying to amend the constitution in that case to make encryption illegal, not the investigators. They're agent

Well it should be the victim or victim's family lobbying to amend the constitution in that case to make encryption illegal, not the investigators. They're agents of the government who are supposed to do their job with the current legal tools at their disposal. They are not supposed to be victim's advocates. In some cases there is no victim, like in drug possession cases.