Much is made of the burn on D.A. Purcell's hand. And, earlier, after the bombing, a policeman is asked to collect the spilled mercury, with the caution, "Don't burn yourself." While it is not safe to touch, mercury will not burn you. Breathing the vapour is especially dangerous. It will make you "as mad as a hatter", a phrase deriving from the days when milliners used mercury to make hats and breathed in the vapour, which caused mental illness, amongst other problems.
Near the end, the crooked lawyer lady gets into her car and then the blind man climbs in the passenger side door. How did a blind man find her car without help and how did he know when she got in the car.
Steve mentions the bomb had a weight activator that had to be triggered prior to the mercury switch activating the bomb. The briefcase was placed under the seat, which was held off the floor by a frame, so it would not have been subject to any weight where it was placed. As such, the bomb would never have detonated and no murder would have taken place.