Was Keith O'Brien still a member of the College of Cardinals at the time of his death?
Yes, but he did not exercise his rights or duties
No, he was expelled
No, he resigned
Yes, and he maintained his duties fully
Answer
Yes, Keith O'Brien was still a member of the College of Cardinals when he died. However, he had resigned as Archbishop of St Andrews and Edinburgh in 2013 amid allegations of sexual misconduct and had chosen not to participate in any Vatican activities or meetings since then.
The Remarkable Life of Keith O'Brien: A Scottish Cardinal's Journey