I can't see how the pilot can be charged with murder whilst taxiing.
If someone stands in the way of the aircraft and tries to force it to stop (other than a marshaller) then it is unlawful interference or an aircraft i.e. hijacking.
The only other alternative is an accident.
If you were in a gyro and decided to kill someone, how are you going to hit them with something behind you? It seems to me the man ran into the back of the gyro, and the pilot probably never even saw or heard him.
Actually you can taxi towards someone and the person would still be hit by the rear pointing propeller as the width of the prop is wider than the gyrocopters fuselage.