A FLT CREW DSNDED 300 FT BELOW ASSIGNED ALT.

Narrative

FLYING THE TRINITY 1 APCH INTO HOU. WE HAD JUST REACHED ELLIN INTXN AND WERE TURNING TO AN ASSIGNED HDG OF 305 DEGS WHEN WE WERE CLRED FROM 7000 FT TO 6000 FT. THE ASSIGNED ALT WAS ACKNOWLEDGED AND THE CAPT INITIATED THE DSCNT. AT THE SAME TIME; THE CAPT WENT OFF FREQ TO HAVE THE FLT ATTENDANTS 'SECURE THE CABIN.' THERE WAS SIGNIFICANT WX IN THE AREA AND I CONTINUED TO ADJUST THE RADAR PRESENTATION TO ENHANCE AVOIDANCE CAPABILITY. JUST PRIOR TO THE CAPT RETURNING TO FREQ; I MADE AN ADJUSTMENT TO THE RADAR WHICH IS LOCATED ADJACENT TO THE ALT SET KNOB. JUST AS THE CAPT CAME BACK ON FREQ; ANOTHER ACFT WAS CLRED TO 3000 FT. I DO NOT RECALL IF IT WAS ACKNOWLEDGED OR NOT BY THE OTHER ACFT. THE CAPT STATED; 'I'M BACK' AND DEPLOYED THE SPD BRAKE. I WAS CURIOUS AS TO WHY IT WAS DEPLOYED WITH ONLY 3000 FT TO GO UNTIL LEVELOFF AT 6000 FT. AS WE REACHED 6000 FT THE CAPT STILL HAD A DSCNT GOING AND I REMINDED HIM OUR CLRNC WAS TO 6000 FT ONLY. HE IMMEDIATELY RECOVERED TO 6000 FT. I DID NOT OBSERVE THE CAPT'S ALTIMETER; BUT MINE REFLECTED A LEVELOFF AND RECOVERY FROM 5760 FT. AS WE WERE PASSED TO THE NEXT FREQ THE CTLR STATED HE HAD NOTED A DSCNT BELOW OR TO (UNSURE OF HIS EXACT WORDS) 5700 FT. NOTHING ELSE WAS SAID BY THE CTLR. WITH THE NUMEROUS THINGS GOING ON (RADIO FREQ CHANGE; CAPT OFF FREQ; MY HANDS WORKING NEAR THE ALT SET KNOB; WX; A CLRNC TO 3000 FT FOR ANOTHER ACFT) I FEEL THE CAPT FELT SURE HE WAS CLRED TO 3000 FT. I FELT OUR BACKING EACH OTHER UP AND THE CAPT'S QUICK RESPONSE TO REMEDY THE SIT PREVENTED A SERIOUS INCIDENT.