  We studied anomalous Josephson effect (AJE) in Josephson trijunctions
fabricated on Bi$_2$Se$_3$, and found that the AJE in T-shaped trijunctions
significantly alters the Majorana phase diagram of the trijunctions, when an
in-plane magnetic field is applied parallel to two of the three single
junctions. Such a phenomenon in topological insulator-based Josephson
trijunction provides unambiguous evidence for the existence of AJE in the
system, and might provide an additional knob for controlling the Majorana bound
states in the Fu-Kane scheme of topological quantum computation.
