FBI Agent Sparks testified as the first witness in the government's case-in-chief. His testimony provided an overview of the government's case, setting forth for the jury the script of the testimony and evidence the jury could expect the government to present in its case-in-chief. He expressed his opinion, based on his training and experience, about the nature of the investigation conducted in this case. Ds were eventually convicted and on appeal challenged the usage of an overview witness improperly permitted the government, over defense objections, to elicit FBI Agent Sparks's opinions about the charged crimes, the reasons for appellants' actions in various circumstances, the nature of the charged conspiracy and the relationships between co-conspirators, including the cooperating co-conspirators who testified as government witnesses, and the strength of the evidence - all before the government had presented any such evidence.