Hi there, looking for some advice re the below:

Colleague was involved in a physical incident at work and went home, assumption at the time was that this was due to physical injury from the incident. Colleague calls in sick for the rest of the week, handing in sick line from GP stating stress at work. 

RIDDOR criteria not met at this point.

Over a week later colleague claiming to have phsyical pain from the injury although this was not detailed in the sick line from the GP.

Do I take the colleagues word for it or do I go by the sick line from GP?

Would you report as RIDDOR just to be on the safe side?

Staff member has been asked to provide statement detailing the events of the incident but two weeks later this has yet to materialise. 

2 parts to your question, im not going to deal with stress here as two complicated and lots more detail needed.

With the physical incident at that caused the alledged injury? You have to decide if it was work realted, so if it was two people fighting over their respective football teams then its not work related for RIDDOR, if it was an argument out of some work - say a manager tumping somene because they did not follow an insruction (used to be very common in car industry im told) then it is work related. 

Remember you can self certify for 7 days, and you could even be on holiday after an incident, the key is are they able to do tier normal duties 7 days after in injury - so a Dr note is irrelevant, so you may have to take thier word - but remember 14 days to report so keep digging. (different for the Dieasease part of RIDDOR)