In verse 18 we finally see the fulfillment of the reference in the header to Alma Chapter 9 that Alma and Amulek would be cast into prison. Soon we will see the fulfillment of the miraculous delivery. In the meantime, Mormon continues to describe the conditions of their confinement.
Alma and Amulek are questioned and physically beaten and thrown into prison. When they are brought out, it is to face the lawyers and teachers. These were the political and religious leaders of Ammonihah, and it was they who taught and enforced the law as understood through the Order of the Nehors. Although they are questioned, they say nothing. That description is repeated in verse 18 and 19, indicating that regardless of the questioning, they firmly declined to say anything.
We saw in the trials of Nehor and Amalikiah that there were confessions given prior to execution. Although the text appears to indicate that they were voluntary, it is possible that these intimidation methods were intended to elicit confessions from Alma and Amulek through less than voluntary means. Thus, their remaining silence prevented the lawyers from even twisting their words into a confession that might allow the lawyers to convict them and sentence them to death.