james the best thing u could do with reserch is to check it after every new suspect u got. then u know who NOT to ask about alibi.
u always find some1 with the reserch so keep on looking for names till u get 1.
anyway there is fixed amount of suspects per level so u can always count them and know if u miss any.
the amount of false vs. true alibis is also fixed so if u count that u will disscover u dont need to check all the alibis. that will save u questions with important witnesses :)