I think in the case of complicated alibis, they're more difficult to verify. Obviously the more complicated the alibi, the more work to verify each detail.
It may very well be that both BB and RB have rock solid alibis and they are completely innocent. But even us lay people have to admit they're both pretty complicated. Nailing them down involves verification of domestic air travel, lodging reservations/check-ins/outs, charter outfitters, restaurant and club eyewitnesses, receipts, car rental agencies, mileage tracking, cell phone activity, cell phone inactivity, browser and social media history, on and on, over four states. That will take time.
Personally, I'm always very suspicious of a complicated alibi. The thing that I find so curious about BB's alibi in particular, is how much effort he has put into it. More than just "out of town" during the crime, he actively reinforces details of the alibi. Before his trip, he used social media to post travel plans, anticipation, weather problems, and flight delays. When he finally left, he posted more on delays arrival times. He later posted details of his activities while there - restaurant, etc. When he returned to Midlothian, he talked to media about the phone calls he placed to his wife from Mississippi, about charter boat plans, about his drive and arrival back to Midlothian - each detailing exact times. He continues in nearly every single interview to casually throw out these kinds of details whether he's been asked or not. He makes sure to stress his rental car had "Mississippi plates", note the time and location he received the news, how law enforcement has "everything" (airline tickets, receipts, etc). He has hinted at his poor health - another possible facet of an alibi. He hasn't talked much but when he does, most of it seems to be laying out and reinforcing a timeline and location that would be inconsistent with his involvement. He really wants to make sure people are aware of his whereabouts. Not a sign of guilt, necessarily. Just something I've found curious.
