From what you are saying it looks like you have been disciplined with a form of written "warning" that's been recorded on your file. Ordinarilly a well-managed employer would have a legally compliant disciplinary procedure in place that sets out types of misconduct and the procedure to be followed. However, if there isn't one in place, the employer will, of course, still have to act reasonably and in accordance with the law.
For an employer to justify that disciplinary action was appropriate, he must have reasonable grounds for believing that the employee committed the alleged misconduct and that this resulted from an investigation that was reasonable in the circumstances. The employer must also carry out a fair disciplinary procedure and the employer must be able to show that any sanction levied was a reasonable response that a reasonable employer would impose.
An investigation is not required to involve any prescribed level of detail or contain any mandatory elements (such as interviewing all involved), it just needs to be reasonable and proportionate. If the investigation leads the employer to believe that the misconduct occurred then the employee should have an opportunity to attend a hearing to answer the allegations. They have a statutory right to be accompanied and must be given notice of the hearing. The employer must then take the employees submissions into account before reaching a decision. If they decide to impose a disciplinary sanction, it must be appropriate in the circumstances and have consideration to the employee's service record.
Therefore, to summarise, the employer does not have to satisfy a burden of proof to discipline an employee but he must justify that the sanction was fair and, in order to do this:
- the employer must carry out a reasonable investigation;
- follow a fair procedure;
- have a genuine belief that the misconduct occurred;
- and levy a reasonable sanction that a reasonable employer would levy in the circumstances.
If this has not occurred and you have simply received a written warning that has been registered on your employment record, you could consider appealing the disciplinary action on the basis of the total lack of any investigation. To answer your question, failing to carry out any real investigation is not good management but whether you appeal will be your decision (you should be mindful that you have provided an unreserved written apology to your colleague).
I hope this answers your question. If so, please don't forget to rate my answer so that I can obtain credit for my work. Our conversation won't end and you can ask me any further questions you need to clarify the above.
Is there anything else I can do to help you with this?
Do you have any further questions?
Just let me know if you do and please do take a moment to rate if you are satisfied.