Sir,
As one who volunteers to pick up litter, I came across a receipt listing goods that matched the nearby empty plastic bottles and a cake box lying on the roadside verge, all recently bought from a local shop.
The goods were paid by a debit card, which only shows the last four digits of the account number. If it was a Silent Witness serious crime scene, I’m fairly certain that the person(s) could be traced back to the shop, probably having CCTV, transaction records, forensic evidence (fingerprints, DNA) and so on.