THE FO OF AN MLG FAILED TO MAKE A XING RESTR ON DSCNT DUE TO CAPT NOT INFORMING THE FO OF THE AMENDED DSCNT CLRNC WHEN LEAVING THE COCKPIT.

Narrative

WHILE PERFORMING PNF DUTIES ENRTE TO DTW; I CHKED OFF CTR FREQ TO MONITOR DTW ATIS. WHILE I WAS OFF CTR FREQ; THE CAPT RECEIVED CLRNC TO DSND FROM CRUISE ALT TO 15000 FT MSL BY 50 MI S OF DJB VOR. WHEN I COMPLETED COPYING DOWN THE ATIS INFO; I RESUMED MY NORMAL PNF DUTIES OF MONITORING CTR FREQ. THE CAPT HAD STARTED THE DSCNT TO 15000 FT MSL. HE LEFT THE COCKPIT FOR A COUPLE OF MINS TO ATTEND TO PERSONAL PHYSIOLOGICAL NEEDS. HOWEVER; HE DID NOT TELL ME ATC HAD INSTRUCTED US TO BE AT 15000 FT MSL PRIOR TO 50 MI S OF DJB. CONSEQUENTLY; OUR ACFT PASSED THE 50 MI S OF DJB POINT AT 16000 FT WHILE CONTINUING TO DSND TO 15000 FT. THE CAPT RETURNED TO THE COCKPIT AT THIS TIME. THERE WERE NO CONFLICTS WITH ANY OTHER ACFT AND THE CTR CTLR MADE NO MENTION OF OUR ACFT BEING HIGH PASSING THE 50 MI S OF DJB POINT. THIS PROB COULD HAVE BEEN AVOIDED IF THE CAPT HAD MADE CLR THE 15000 FT MSL ALT RESTR HE HAD RECEIVED WHILE I WAS OFF CTR FREQ WAS TO BE MET BY 50 MI S OF DJB VOR; PRIOR TO HIS LEAVING OF THE COCKPIT. I COULD HAVE QUESTIONED HIM ALSO BEFORE HE LEFT THE COCKPIT TO CLARIFY THE CONDITIONS OF THE ALT RESTR.