the HR department has since requested an outlook appointment. I will
have to attend this in a few days.
You need to reframe this and stick with your frame. Do not let them impose their frame.**
In view of a number of comments criticising my answer I have decided
to add this panel to address some of them. Forgive me for using a
"quote" box. I'll look for a better format.
Some people have read my suggestions as aggressive. They are not intended to be. I suggest an air of mature and considered concern for
the well-being of yourself and the company. Speak politely but firmly.
Suppose the OP has done something that the company as a whole disapprove of. Answering, Yes I did do it, will likely get you sacked
anyway. So why admit it? Rather deflect by asking who said this and
make your intention clear that such doxxing is not acceptable and you intend action.
My main intent was mainly to recommend reframing as a technique, rather than slavishly do what I would do. You can guarantee that the HR panel that you meet will have got together to discuss their approach (their frame). If you walk in unprepared, you will be like a lamb to the slaughter.
Reframing can be anything you like.
Invent a strong positive frame and don't be diverted from it by theirs. The
whole point is to avoid being purely defensive, instead have some agenda
of your own for the meeting. Walk in feeling secure in your position
and challenge theirs tactfully if necessary.
I'll add some links. They are of varying quality but they explain
framing from the point of view of managers as well as in general life.
The following is presented in a 'popular' way and may not be 100% orthodox but it is helpful in my opinion and remarkably mirrors the OP's question in some respects. It's worth watching until the end.
What follows is my personal approach. Of course it should be modified as necessary and take into account employment law in the region where you work.
I would speak first and as soon as you sit down (or before if necessary) say,
"Thank you for arranging this meeting it is very important for me. I understand that someone may have been spreading rumours about me. If this is true I may need to contact the police. Therefore I will be very glad of any information you can give me. I'm sure the company does not want its employees to be attacked in this way. It is bad for the employees and it is bad for you. If I find out that someone has indeed been spreading such rumours, I may need to consult a lawyer with the aim of suing that individual"
In other words, go into the meeting presupposing that it is for your benefit. Treat it as information gathering for you. Prepare a list of questions to ask them and don't be put off. If they ask you questions, simply say, "I'm sorry I am not going to answer unsubstantiated claims by an anonymous person. You must tell me your source and precisely what they are accusing me of so that I can take the necessary action."
If they tell you, don't confirm or deny (as per the politician's interview technique) just thank them for the information and tell them what action you intend to take - lawyer, the police etc. Then thank them and leave. You may wish to say, "I'll let you know what happens" or you may not.
If they say they cannot divulge the source then say "Then why have you invited me here? It is vital information so that I can protect myself from unsupported rumours. If you refuse to tell me will you at least agree to tell the police?"
I typed this quickly and it may come across as abrupt. However make sure you play good cop with them and be scrupulously polite. Expect answers from them and make sure you get them. This is a technique used by expert interviewers - you need to be the expert. You can do this by preparing, anticipating everything that may come up and then reframing it to your benefit - always imagine yourself as being in charge.
Take charge. Ask questions. Don't answer questions, just say your intended actions. Take it out of their jurisdiction and into that of the law.
P.S. Do not let them regain the frame. If they ask you "Did you do it?", answer "I'm sorry that is not the subject of this meeting. The important thing is that you give me the information I need so that I can take the appropriate steps. If they counter that it is the subject of the meeting then say. "No. This is very important to me the matter is out of your hands I must deal with this in the proper way. If they say "This is the proper way, say "I think you need to understand that etc." and have that argument prepared. Don't back down or you are immediately on the back foot. If you do retreat for a moment, simply ignore and return to questioning them.
P.P.S. Take a notebook. Have it on the desk in front of you. It will have your list of questions. Ask one then look up with your pencil hovering over the notebook. Maintain silence and an air of expectancy that they will answer. Tough it out. Make them break first. If they answer, say Uhuh. Write some notes and ostentatiously tick off the question. Before they have time to think ask the next question. You need an out. As I suggested, when you have ticked off the last question, stand up and say, "Thank you you have been a great help but I may need more information. I'm sure you will be willing to help if I need a further meeting. Then walk out.
P.P.P.S - Your first question might be, "How long do we have for this meeting? I have some important questions to ask and I need to get through them before my next appointment (of course there must be a next appointment to say the last phrase)."
**Reframing is an important skill. Obama was adept at it. There are all sorts of uses for it including in mental health but if you search online, you will eventually find explanations about how to use reframing tactically. I'll see what I can find.