There are two IT experts. The first is an IT Security Manager. The only IT Security Manager of that name I have found is not employed by Fife, but it may be that Fife outsource some of their IT services to his employer. The other is an expert in mobile phone forensics, so is presumably the person who examined Upton's phone.
As far as we know, both have been called by Fife. We aren't going to hear a great deal from either of them as each of them will be questioned by JR for 30 minutes then NC for 30 minutes.
I don't know for sure, but the most likely reason for calling the IT Security Manager is to talk about how Fife have handled their disclosure obligations and possibly to try and justify their repeated failures in this regard.
The brief time each side wants to question them suggests we aren't expecting any major bombshells from either.