A dean's certification is a little nightmare that requires you to strong arm your former educational institutions into sending a clearance to law schools requesting them. After having mine "lost in the mail" THREE TIMES I wanted to head to my UG with a baseball bat and roll some heads. My advice: Be firm -- and ask for the names of whoever is filling these out for you. This helps! Keep fax records or do certified mail, too. Also, if your dean ends up submitting them past the deadline for admission I would have him/her call the admissions office and explain the circumstances.
Sorry for the rant. These have truly been the BANE OF MY EXISTENCE!
As an aside, Brooklyn processed my admission without the dean's certification. Although I would bet that they require it before you're allowed to fully matriculate.