What information should you consider in judging a person's character?

Yes, you are right to consider the data as indications that you need to find out more about the two people. It may be possible to make small changes in your relationships with these people to reduce the risk of harm to you, until you can find out the truth (if you ever can). I was in a difficult situation a few months ago with two employees. A fairly serious mistake was made, and each employee blamed the other. Unfortunately, this was not a situation where there could be two different but valid viewpoints. One of the employees was lying. It was impossible to find out which one was telling the truth, so all I could do was be aware that there was a problem, and watch both employees a bit more carefully for a while, to make sure similar mistakes were not made again. I tweaked the work flow slightly and told the higher-paid and more experienced employee that she would in the future be responsible for making sure mistakes didn't happen again. I also had heart-to-heart talks with the employees and explained why it's better to tell the truth about a mistake than to lie about it. These employees both seem to be doing well so far.