Historian interviews two people who fought during a certain battle during the Gulf War. One person says U. S. forces fired first; the other person says Iraqi forces fired first. To try to learn what really happened, the historian should:

If both parties involved are blaming the other for the start of the battle, the historian should try to get the statement of a 3rd party witness, preferably one that is impartial and a first-hand witness. This makes the 3rd party witness more credible. This also avoids any self-serving motives of the the US and Iraqi forces.