Are reports of Human Rights Watch reviewed by external authorities before they are published? Who verifies the veracity of the information present in their reports? Are evidences and citations presented in these reports audited?
Are reports of Human Rights Watch reviewed by external authorities before they are published?
They probably try, but it's often not possible to determine if testimony is authentic or not. The New York Times has an article in which the founder of Human Rights Watch, R.L. Bernstein, explains the difficulty:
But how does Human Rights Watch know that these laws have been violated? In Gaza and elsewhere where there is no access to the battlefield or to the military and political leaders who make strategic decisions, it is extremely difficult to make definitive judgments about war crimes. Reporting often relies on witnesses whose stories cannot be verified and who may testify for political advantage or because they fear retaliation from their own rulers.
If they have additional evidence to back up some claim I'm sure they put it in (if at all possible) because that improves their report. If there is no additional evidence mentioned in the report / article then I think you should assume the worst: a single source that has not been verified.
The reports and accompanying pictures of Human Rights Watch are not reviewed by independent institutions or authorities to validate their truthfulness and authenticity.
The CEO of Human Rights Watch, Ken Roth and his wife Dr. Annie Sparrow, are proven to have used faked images respectively misattributed images to support their claim of atrocities being committed by government forces in Syria.
HRW can be seen as a part of the propaganda media machine in the aim to force a regime change in Syria.