ALT OVERSHOT ON DSCNT.

Narrative

THIS INCIDENT POINTS OUT THE VALUE OF SOMEONE FLYING THE AIRPLANE WHILE 1 CREW MEMBER BRIEFS FOR THE APCH. WE HAD BEEN CLRED TO DSND TO 12000 FT. THE FO WAS BRIEFING FOR THE APCH AND I WAS WATCHING THE AIRPLANE. THE FO READ A XING ALT FOR THE FAF THAT I DID NOT RECOGNIZE; SO I LOOKED DOWN AT MY CHART TO CHK THE CORRECT ALT AND ADVISE THE FO. AS A RESULT; WE DSNDED THROUGH 12000 FT TO APPROX 11500 FT; AT WHICH POINT BOTH OF US CAUGHT THE ERROR AND INITIATED A CLB BACK TO 12000 FT JUST AS ATC QUESTIONED OUR ALT. WE RESPONDED THAT WE WERE IN THE PROCESS OF CORRECTING THE OVERSHOOT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE DC-9-30 FOR AN UPSTART ACR. PREVIOUS TO THIS; HE HAD BEEN FLYING THE SAAB 340; AND PRIOR TO THAT; DC-9'S FOR A FAILED ACR. HE ADMITS THAT THE APCH BRIEFING WAS TOO LATE. HE WAS DISTRACTED BY A WRONG STATEMENT IN THE FO'S BRIEFING AND TURNED AWAY FROM THE INSTS AT THE WRONG TIME. THE FO WAS NEW TO THE ACFT AND THE ACR; AND THE RPTR HAD NEVER SEEN HIM BEFORE. THE FACT THAT THE FLC HAS TO LEVEL OFF THE ACFT WHILE ON AUTOPLT; RATHER THAN LET THE ACFT DO IT ITSELF AS IN THE SAAB; 'CREEPS INTO THE EQUATION OCCASIONALLY.' THE RPTR HAS NOT HEARD FROM THE FAA ON THIS INCIDENT.