Law enforcement procedures

Connecticut State Trooper Glover was working as an undercover officer in narcotics. He and an informant went to an apartment building in Hartford, where Glover knocked on the door of one of the apartments. A man (the defendant in this case) opened the door and in a 5-to-7 minute period sold $20 worth of heroin to Glover. Glover had never seen the defendant before and did not know the defendant's proper name. Upon leaving the building, Trooper Glover described the man to Officer D'Onofrio, who had been backing him up outside the building. From the description, Officer D'Onofrio suspected that the seller was the defendant. D'Onofrio obtained a single photograph of the defendant and left the picture at Trooper Glover's office. Two days later, Glover viewed the single picture and identified the defendant as the man who sold him the heroin. Based upon this information the defendant was arrested. Without defense objection, the picture was used as evidence, and Trooper Glover made a positive in-court identification of the defendant.

What improper procedure was used by the officers that caused the defense lawyers to appeal this case to the U.S. Supreme Court? Should the evidence of the in-court identification be allowed, and should the defendant's conviction for selling heroin be affirmed? Why?