Set the timer for six minutes. The first member of team one will present her opening argument for that six minutes. When the timer is up, the member must stop her presentation.
Set the timer for six minutes. Allow the first member of team two to present his opening argument for that six minutes. When the timer is up he must stop his presentation. Set the timer for three minutes and let the audience cross-examine both presenters.
Set the timer for five minutes. Let the first member of team two present his argument further. When the time is up, set the timer for three minutes. During this three minutes the first member of team one can cross examine the first member of team two. When this three minutes is up, set the timer for another three minutes. During this time the audience can cross examine the first member of team two.
Repeat steps 1 through 3 with the second members of teams one and two.
Set the timer for five minutes. Let team one make its closing arguments. Once the five minutes is up, set the timer for five more minutes and let team two make its closing arguments.