My son has been terrorized by the local law in our small town in his teen years and i learned a good phrase from him which is neither saying yes or no to a search and that is, "that will not be necessary". Once they ask to search 3 or 4 times and giving the above response 3 or 4 times is neither offensive or consenting and tends to satisfy the officer.
I heard a driver talking on the CB yesterday, so i know it must be true LOL, but he sounded sincere. He was asked to bring his papers in at the scale, left his truck unlocked and while walking to the office a DOT man walked over to his truck and begin to enter and do a search. Driver said he immediately went back asked him what was going on and the officer said as long as the door is open (read unlocked) he can search a CMV without consent. Driver told him OK, but you may only search the front cab, not the sleeper. DOT told him if the curtain is open, I can search the complete truck and take anything he wants that is not supposed to be there. Driver recommended always locking your truck and pulling curtains shut when exiting truck. Sleeper is living quarters, not commercial, when curtains are pulled, or so driver says.
The only time I have been searched was in my '74 Camaro, 16 yrs old, wet behind the ears, in 1974, two separate occasions, asked to open my trunk. 1st time, Sherman, TX on our way to Texoma, I had a case of Coors in the trunk after telling the officer I did not have any more alcohol, but luckily it was still in place tucked under the quarter panel and covered with the newspaper I always used to line my trunk with. Officer asked me what was in the brown bag and I gladly showed him it was clothes and a toothbrush for the weekend. 2nd time, Dallas, TX, officer said there had been burglaries in the area recently and wanted to check my trunk. Nothing in the trunk, but I had a few full bottles rolling around on the floor board behind the driver's seat he never saw, WHEW! This was back in the day when a search of the passenger compartment was fairly rare, remember those days? Both times I was stopped for speeding, ticketed in Sherman, Dallas officer gave a warning justifying it must be hard to keep the Camaro under 60 in a 30 hehe.
I find it always goes a long way with LEO's to give them your utmost respect. Usually works for me, until it doesn't......