The plain feel doctrine allows a police officer to seize the objects during an otherwise legitimate pat-down search if by plain feel he reasonably believes to be contraband.
The plain view doctrine applies by analogy to cases where a police officer discovers contraband by plain feel or touch during an otherwise lawful search.
Objects observed in plain view or by detected by plain touch during a lawful search can be admissible evidence if its incriminating character is immediately identifiable. For instance, a container may be opened if by a touch of the outside, the officer becomes convinced to a reasonable certainty that the content may be evidence.