COMMUTER VFR IN IMC DURING VISUAL APCH TO SAN.

Narrative

I WAS THE PNF ON A FLT FROM LAX-SAN. A LOW PATCH OF FOG OBSCURED THE APCH E OF RWY 27. THE CAPT SAID HE HAD THE FIELD IN SIGHT AND ASKED FOR A VISUAL APCH. THE CAPT SAID HE WOULD MAINTAIN VFR OVER THE FOG LAYER. ON SHORT FINAL (WITHIN THE ARPT BOUNDARY) LIGHTS COULD BE SEEN THROUGH THE FOG. THE CAPT THEN DSNDED INTO THE FOG LAYER. THE TWR ISSUED ORDERS FOR A GAR; WHICH WE ADHERED TO. WE WERE THEN VECTORED FOR THE ILS 9 SAN. AS WE SET UP FOR THE APCH THE FOG BECAME MORE PRONOUNCED. THE APCH WAS FLOWN TO THE DECISION HEIGHT OF 350 FT. THE FIELD WAS NOT SEEN SO WE BEGAN THE MISSED APCH. AS WE BEGAN THE CLB THE CAPT SPOTTED THE RWY LIGHTS AND COMMITTED US TO A LNDG. THE ACFT WAS LANDED ON THE LAST THIRD OF RWY 9. APCH LIGHTS WERE NOT SPOTTED AT DECISION HEIGHT (OVER THE MIDDLE MARKER); LNDG WAS NOT ASSURED WITHIN THE TOUCHDOWN ZONE; AND IT IS MY BELIEF THAT THE VISIBILITY WAS BELOW 1 MI. IN RETROSPECT; I NOW BELIEVE I SHOULD HAVE TAKEN THE ACFT AWAY FROM MY CAPT. I BLAME MY INACTION ON NOT BEING PREPARED FOR HIS DECISION TO LAND AFTER THE MISSED WAS CALLED. I HAVE DOUBTS ABOUT MY CAPT'S ABILITY TO CONDUCT SAFE OPS IN MARGINAL CONDITIONS. I HAVE ALERTED MY CHIEF PLT OF THE EVENTS; AND I AM WAITING FOR THEIR ACTION.