Equip the back seat of your squad with an audio transmitter. Most departments have extra transmitters/mics from old in-car video camera systems. If not, you can purchase one fairly cheap. Most have a 1,000-foot range, which is more than enough. Conceal the mic in the headliner of back seat. Conceal the transmitter box at top of partition between front and back seats. Make sure the box is not visible in such a way to allow the red LED ‘transmit’ light to anyone in the back seat.
Activate the transmitter and place suspects in back seat together. Be sure to turn off radios, etc. Now, monitor the suspects’ conversation real time via a scanner, handheld, or vehicle mount from another unit. One or more officers begin the vehicle search while one monitors and records suspects. Usually when the search officer gets close to the concealment the suspects begin to chatter.
This tech has also worked several times when we stopped the block car instead of the load car. We have been able to ID the load car and chase it down and make the seizure plus a conspiracy case. This technique saves a lot of time wasted going back and reviewing tapes.