Dead Ball or not

[w_sohl]

For those of you that have viewed my "Balk, Ball or nothing" thread, this is the same partner same game.

Towering foul ball down 3B side. Field has a line drawn from the back of the dugout to the outfield fence indicating DB territory. Player runs over to field ball, moves into DBT, realizes that he is in DBT and retreats into LBT. Makes the catch with the ball over DBT. My partner ruled that the ball was dead because he thought the player could not reenter LBT. Now I know a player can have one foot in DBT and one in LBT and still make a legal catch of a ball over DBT. But in this scenario, was this still a legal catch with the player entering DBT and retreating to LBT before the ball was touched or the catch was made and completing all actions in LBT?