Tell your mate to contact the officers as they should be updating him as the case progresses
And if you have worries tell them they will give you all the support you should need !!
Your mate should have been explained all the special measures we can put in place to help get his evidence...
like screens in court so they cant see your identity, voice masking , giving evidence from a court in another district....the list goes on
Also your mate can be ordered to court if they feel they need his evidence !!!! ( even after he has retracted )