THE ACCIDENT OCCURRED DURING A ROUTINE CIVIL AIR PATROL (CAP) FLIGHT CHECK. THE PILOT-IN-COMMAND (PIC) WAS THE OWNER OF THE AIRPLANE AND A CAP MEMBER. THE CHECK PILOT WAS ALSO A CAP MEMBER AND A CFI. THE FLIGHT PROCEEDED NORMALLY UNTIL A SIMULATED EMERGENCY LANDING. THE CFI SAID THAT THE PIC MADE AN APPROACH TO A SMALL AIRSTRIP AND ELECTED TO SLIP THE AIRPLANE TO LOSE ALTITUDE. HE SAID THAT THE PIC INADVERTENTLY STALLED THE AIRPLANE AND ENTERED A SPIN, COLLIDING WITH TREES BEFORE A RECOVERY COULD BE MADE. THE CFI SAID THAT HE DID NOT HAVE A FLIGHT CONTROL STICK IN THE REAR COCKPIT; HE SAID THAT THE PIC TOLD HIM THAT HE DIDN'T HAVE ONE IN THE AIRPLANE. AN UNDAMAGED SPARE FLIGHT CONTROL STICK WAS FOUND IN THE WRECKAGE ALONG SIDE THE REAR SEAT, AND THE CFI SAID HE WOULD HAVE INSTALLED IT IF HE HAD KNOWN THAT IT WAS THERE. THE CFI SAID THAT NEITHER CAP NOR FAA REGULATIONS REQUIRED DUAL FLIGHT CONTROLS FOR A NON-INSTRUCTIONAL EVALUATION FLIGHT.