I spent a few min reading the referenced paper, and they do seem to demonstrate that there's the possibility of electronically compromising car electronics, including brakes.
However, steering and brakes are mechanical systems in Hastings' 2013 Mercedes C250 (like almost every other car), and cannot be electronically overridden. The steering wheel is connected directly to the wheels, and can't be controlled by the electronics. Electronics can activate the brakes, but can't cause the brakes to not activate because the pedal is connected hydraulically to the calipers. Even if the engine is racing, braking force is greater than the engine's force. [2]
If his car was vulnerable, all-electronic attack doesn't seem like a good way to assassinate someone if they can simply step on the brakes to stop the car. Changing the mechanics to allow remote control might be possible, but that's a lot of physical evidence to add to the car.
However, steering and brakes are mechanical systems in Hastings' 2013 Mercedes C250 (like almost every other car), and cannot be electronically overridden. The steering wheel is connected directly to the wheels, and can't be controlled by the electronics. Electronics can activate the brakes, but can't cause the brakes to not activate because the pedal is connected hydraulically to the calipers. Even if the engine is racing, braking force is greater than the engine's force. [2]
If his car was vulnerable, all-electronic attack doesn't seem like a good way to assassinate someone if they can simply step on the brakes to stop the car. Changing the mechanics to allow remote control might be possible, but that's a lot of physical evidence to add to the car.
[1] http://www.autosec.org/pubs/cars-usenixsec2011.pdf [2] http://www.keacher.com/672/title-fight-brakes-versus-engine/