Puzzle #200: Whodunnit?

Four suspects were questioned by police about a recent crime. It is known that one of them must have done it. Each suspect made two statements. One person told the truth both times, one person lied both times, and the other two told the truth once and lied once. Given the following statements, whodunnit?

Al: (A1) I did not do it.
(A2) Di did it.
Bo: (B1) Al or Ci did it.
(B2) Di is being totally truthful.
Ci: (C1) Bo is totally lying.
(C2) Di did not do it.
Di: (D1) I did not do it.
(D2) Al did it.

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, April 5, 2017 at noon Pacific Time. I will post the answer shortly after.