Col Robert Smith was the Justice of peace and also captain of the Carthage Greys. He opposed The Prophet Joseph Smith and the Latter Day Saints. He presided over the case tof the Expositor being destroyed in Navuoo in June 1844. He walked out of the courtroom without hearing the additional charges against Joseph Smith and Hyrum. This meant the Prophet and his brother were still under arrest while the others were free. Col. Robert Smith was in charge by the Governor Ford's order to command the carthage Greys to guard the jail. Col. Robert Smith was the one who sent Col. Levi Williams in charge of the Warsaw militia ( who had been told by the Governor to disband)the information that his men was guarding the prsioners and the Governor was on his way to Nauvoo.
The jail was attacked by a mob the guards let them in without a fight and the Prophet Joseph Smith and his brother Hyrum were murdered .
This information can be found in a book called Nightfall at Nauvoo by Samuel Taylor.
You should be able to find out more information on Col. Smith through the library or the Hancock Historical Society.