I assume that you are referring to either a grievance hearing instigated by the employee or alternatively it was a disciplinary hearing which the employee was required to attend to answer complaints about his behaviour. In reality the law is the same in both situations.
It is customary for both sides to take their own notes. Whilst Employment Tribunals like both parties to agree an accepted version of the notes this is rarely possible.
Even if the transcribed notes accurately reflect each parties’ handwritten notes there is no guarantee that the two handwritten sets agree. Clearly shredding original notes can be portrayed as having a sinister significance and it is better not to do it until all chance of litigation has passed.
The Data Protection Act 1998 does not lay down any particular length of time for data to be held. It does state that “personal data…shall not be kept for longer than necessary…” There is at least one further reference to timescales in the Part 1 Code regarding the retention of applicants’ details, who are not called to an interview, which states that such details should not normally be held for longer than four months. As a Code it is not law but only guidance.
However, four months is undoubtedly a too short a period since an investigation of discrimination can be brought in exceptional circumstances for up to five years after the event complained about. For most employers keeping such information for up to a year would be more reasonable, justifiable and safe.
With specific regard to notes of disciplinary/grievance hearings it would be prudent to keep all original documents for at least six months after the employment has terminated and probably no longer than a year.
It is not uncommon for one set of legislation to contradict another. Whilst your HR Manager may have behaved unwisely, they have not actually broken the Data Protection Act.