Here are Mill's ten red flags:
1. The accuser uses the press instead of the process.Individually, none of these are especially compelling as a red flag. Individually there are occasions when any one of the flags would be well warranted. But, in aggregate they become more indicative.
2. The accuser times releasing the accusation for an advantage.
3. The accuser attacks the process instead of participating.
4. When the accused’s opportunity to mount a defense is delegitimized.
5. The accuser seeks to force the accused to defend himself or herself before committing to a final version.
6. The accused makes a strong and unequivocal denial.
7. The accuser makes unusual demands to modify or control the process.
8. When the accuser’s ability to identify the accused has not been properly explained.
9. When witnesses don’t corroborate.
10. When corroborating witnesses simply repeat the accusation of the accuser but don’t have fresh information.
This feels related to my post How to assess a piece of writing, especially outside one's expertise. There is a difference though. In that post, you are estimating the value of the evidence presented. Mill is upstream a bit, not assessing the argument per se, but the predicate claim. Seems like splitting a hair but it makes sense. It is the difference between the headline of an article and the substance of the article itself.