Wow, someone downvoted within seconds of me posting this. Could you maybe at least read the answer completely before you vote?

Probably a close-question-downvote-answer bot.

@Philip, thank you very much for your answer. Bob definitely resides in the first case as I said earlier. He is a very professional, honest, and ethical. But you didn't provide way in which Bob can surely prove himself innocent. This is disturbing because he is about to lose his job, that he loved, because of something he didn't do!!

@Raykh The answer, point 3, happen fast. At my job, a coworker was meet with the HR because he, without thinking to it, touched someone else shoulder to let her pass first the door. The contact was too much in this case. There is a unwritten ethical's rule to keep a 4.5 feets distance with someone you don't fully know, as else the other person can seen you too near them.

@yagmoth555 when you say The contact was too much you mean like a lot of grip on the touch or normal touch? And... you kidding right?

@Raykh It's a he-said-she-said situation with no witnesses and no evidence, so Bob can't prove himself innocent. But the good news is that Alice can't prove him guilty either. So the outcome of the situation depends on whose story seems more believeable. As I wrote: "Bob might want to deny and look for motives why Alice would go to these lengths just to harm him". Arguing that Alice would benefit somehow from him getting fired is no proof of innocence, but at least makes his hypothesis that he is being framed more plausible.

@William-H-M If you are referring to the 4.5 feet distance with "you are kidding": There is actually interesting research regarding which physical distance is the social norm for which grade of familiarity. The distances vary a lot between different cultures. If you refer to being touched at the shoulder: This is indeed dangerous. The only intentional physical contact you can safely initiate in a work environment is shaking hands. With everything else, assuming consent is dangerous. Not everyone will feel harassed, but they might feel harassed and they have the right to be.

@Philipp I was referring to the being touched, the 1.3 mts seems fines to me, seems a little too much for me, but this actually vary a lot between cultures

@Raykh "you didn't provide way in which Bob can surely prove himself innocent." Without knowing all the facts you don't know if he's innocent. He could in-fact be guilty. If you operate on the presumption of being his friend and maintaining his innocence then you can't expect us to bend what little hearsay evidence you provide in your friend's favor. I find the question and scenario a bit unrealistic and unanswerable according to your criteria. This question was closed prior- it should probably be closed again because you ask something that is impossible to prove.

@Raykh Does Bob need to prove himself innocent? Did this happen in a country where the accused is not considered innocent by default, until proven guilty? You don't appear to have mentioned a country or jurisdiction.

@Zorkolot The question is currently how to refute the accusation, not how to prove innocence. The two aren't quite the same thing. If I were accused of robbing a bank and had no alibi, refuting the accusation would not consist of me proving innocence but in showing that their evidence didn't really point to me in specific.

@DavidThornley Lets read what OP specifically wrote again: "you didn't provide way in which Bob can surely prove himself innocent". I think that speaks for itself. Nothing here allows an alibi as an alternative solution.

@Raykh a little story: Before I met her, my girlfriend had a friend who was a nice honest upstanding man, everyone in that group of friends thought so too. One day this man was accused of rape and strongly denied it. The only problem was that he didn't have an alibi, so he asked my girlfriend and friends to tell the police he was with them at the time in question. They agreed to help him, after all he was their friend, a good guy who had been falsely accused. Luckily they never made that false statement, because DNA evidence forced a confession. If you don't know, then you don't know !

@AaronF An unusual situation. Most difficult cases are where one says it was rape, and the other says it was consensual sex, and it's obviously hard to prove. A case where she says it was rape, and he says he wasn't present, that is usually a lot easier to prove or disprove. BTW. False alibi in the UK is "perverting the course of justice" and will usually end in jail. And if say five people are asked, four give an alibi, and the fifth tells the police "he asked the five of us for a false alibi", the friends are in a very bad situation.

Your advice for Stupid misunderstanding assumes that Bob can tell the difference between 1 and 3 AND that Alice is willing to admit that she might have made a mistake.