Courtroom dramas portray lawyers as quick thinking protagonists who can silence any witness with an emphatic "objection!" In real life, however, law practice is more about preparation than speed. Courtroom lawyers prepare for their appearances: they know the evidence that each side will introduce and can anticipate many of the evidentiary issues that will arise. There's no doubt that courtroom appearances require lawyers to think on their feet--but their quick responses usually draw from careful preparation.
Studies of the knowledge and skills needed to practice law competently have never identified speed as a component of entry-level lawyering competence. On the contrary, new lawyers should take the time they need to understand a client's problem, analyze it, prepare documents, and carry out other needed tasks.
For more information about the role of speed in assessing minimum competence, see the page on Speededness in our Problems section.