Is dash cam evidence allowed in an investigation

Generally speaking, yes camera evidence is allowable in court. However, the other side may argue to throw out that evidence because its authenticity cannot be verified. Its up to you (or the state) to put forward evidence that the video was recorded on the date and time in question and was not altered. A slick attorney might be able to throw enough spaghetti against the wall to get some to stick and get the video tossed, but generally it should be allowed.