Field Test is the third story from Batman: Gotham Knight.
An accident involving WayneCom satellite's gyroscopic electromagnetic guidance system ends up with Lucius Fox creating a device with the satellite's gyro and an advanced motion sensor that will electromagnetically deflect small arms fire. Bruce Wayne takes the device and attends a charity golf tournament being held by developer Ronald Marshall. He discusses the mysterious death of a woman, Teresa Williams, who had opposed some of Marshall's plans. During the tournament, Wayne secretly takes Marshall's PDA device. Later that night, as Batman, he hijacks a boat owned by Sal Maroni, and drives it alongside a boat owned by rival gang leader The Russian. He proceeds to attack both gangs at once, with assistance from his new device. He attempts to force a truce between the two gang leaders until he can get evidence against them, but is disrupted when one of Maroni's men fires at him. The bullet deflects and instead hits one of The Russian's men. Distressed, Batman takes the injured man to the hospital. Later, he returns the device to Fox, stating, "It works too well. I'm willing to put my life on the line to do what I have to. But it has to be mine, no one else's."