cleveland , ohio , officer michael brelo is facing two counts of manslaughter .
timothy russell , 43 , and malissa williams , 30 , killed during 2012 shooting .
brelo 's footprints were found on hood of chevy malibu where they died .
rookie said he learned about hood ` because -lsb- brelo -rsb- was talking about it '
judge will decide brelo 's fate and he faces a max sentence of 25 years .