The hearing is your last chance to make sure DTA has the facts supporting your position, including any documents.
The hearing usually takes place at your local DTA office in a separate room. Only the people who need to be there are allowed in— the DTA worker(s), you, your representative if any, any witnesses, and the hearing officer. Everyone who is testifying must do so under "oath or affirmation." The hearing is audio-recorded. 106 C.M.R. §§ 343.450, 343.500, 343.550.
If you believe that the DTA is using evidence that is unfair or unreliable— for example, an accusation from an unidentified person— tell the hearing officer that you "object." Objecting may make the referee think twice about relying on this information. Also if you lose the hearing and appeal to court, the court can consider whether the hearing officer made a mistake by admitting the evidence you objected to.
If you are not receiving benefits, you can ask the hearing officer to decide your case right away with an "interim" (not final) decision.
DTA sometimes holds hearings by telephone or video. This may make it hard to understand what is being said, to see the evidence, and to object. If DTA schedules you for a telephone or video hearing and you want a face-to-face hearing, call and write the Division of Hearings (if you have time before the hearing) and make sure to state on the record that you want a face-to-face hearing.