Self Seal Evidence Bags As Used by National Police Forces and HM Prisons Each bag has a pouch to contain the evidence or sample. This is sealed with a tamper evident strip and all sides of the bag are printed so that any attempt to break into the bag would be obvious. The other end of the bag has a write on panel for sample description, how obtained, date, time and signature. Each bag is uniquely numbered and bar coded for identification and can be presented in court as evidence.