They wouldn't let him take in a family member, which they have the right not to, but took the work colleague aside just before the meeting telling the colleague he could come in but wasn't allowed to speak.
That is correct - you can have a fellow member of staff in an HR meeting, but they cannot speak on your behalf - I think the idea is, that they are there to take notes for you, and so you can then have a pause during the meeting to discuss it between yourselves. I have been said silent person for workmates before, and have had a mate in as my silent partner, whilst in my own HR 'talking to'.
He came to my house to seek advice and while on the phone with the HR person she said that he had logged into his personal Gmail on the "work system" and walked away while leaving it logged in. I don't know much more about it but I assume that someone else at his work must have started snooping into his logged in account and saw that he accesses porn and torrent sites who then reported it.
I am guessing that he must have access to a shared device in the office/shop floor/wherever - and unfortunately, logging into your
personal email on a
corporate device, is likely in breach of any IT Policy he may have signed, or agreed to indirectly, when taking employment. If he had a bunch of spam or 'genuine' emails about questionable content - then whoever discovered the emails, likely assumed he had been looking at that content on the device - and there was probably a bit of a knee-jerk reaction by folks who don't understand PCs.
I'd be looking at the IT Policy in more detail to see if he has broken any rules, as I expect that's all they'll be able to get him on really. As we all know, having a smutty email in your inbox, doesn't mean you were looking at that smut on the device; though he might have to argue this with a tribunal; so he might be best getting ACAS advice - or someone doing that on his behalf?