Had a humiliating experience in Sainsbury. Shopping completed by using SmartShop scanner. Assistant told be I was to be the subject of a 'random' check -14 items - then escalated it to a full check. Started to checked the items in my freezer bag and continued to scan each item as they were emptied from the bag and place them on the floor ( a filthy floor which could contain bacteria, germs and quite possibly animal faeces and probably did) as they didn't have enough room to place them elsewhere (another trolley could have helped but that obviously didn't enter their head. Requested a manager was called and decided to film the assistant but not record her face. Another assistant looked to see what was going on - told it was a full check - and informed us the manager was too busy to attend at that time. When the bag had been emptied onto the floor the search was moved to a supervisors desk albeit cluttered thankfully it was no longer laid out on the floor. The manager arrived told me the checks were random and I wasn't allowed to film in his store. I said I shouldn't be humiliated in his store - he left. Security turned up, asked what was going on and remained whilst the search continued standing in a menacing manner. Search was completed I was then told that she had discovered that I had overcharged myself by scanning 4 of the same items instead of 3 and I had scanned a chocolate bar twice when there was only 1 ! Marvellous this lengthy process had save me £3 ... I was then told that this is the reason they carry out these checks because customers like me sometimes over scan items and they save them money. Fantastic I spend over £140 and Sainsbury find they have found an 2 errors in my favour and save me £3. They must think the public are stupid and cannot see through what is going on. I asked to see a list of the items I had scanned but they are unable to provide that as I hadn't paid for those items and the only list to be given to me is the assistant's dubious list. It was dubious in my opinion as I believe following the inconvenience, they 'rewarded' me with £3. I did contact customer services and spoke to 'R' who insisted that her name was not used who said the Area Manager would be informed and the assistant would probably have to receive further training. I don't really see how further training could help when there was a lack of common sense. I should also mention that Sainsbury claim that 'SmartShop means you'll be able to skip the checkout queues and be on your way in no time' .