Police did not quiz a key witness for a description of a suspect accused of supplying drugs to Croydon teenager Daniel Spargo-Mabbs, a court was told.
Sixteen-year-old Daniel died after taking ecstasy at a west London rave on January 17.
Ryan Kirk, 21, has denied supplying class A and B drugs. His defence counsel, Roderick Jones, told Iseworth Crown Court that a "missed" formality at an identification parade had left police without a certain identification of the suspect.
The court heard how, during the identification procedure, no question was asked for an initial description of the suspect before the parade began.
Giving evidence, Det Con Tracey Wilson, who conducted the procedure, said the initial question "was missed".
Nicqueel Pitrora, 18, from Croydon, has admitted being concerned in the supply of a class A drugs on the day of the rave.
The trial continues.
