Gain entry to his home and from his computer download the most vile child porn images known to man, then make an anonymous phone call to da feds. Obviously alot ground work needs going into this such as his daily whereabouts, who is at home and when etc...
Buy as much heroin or cocaine as you can afford, along with weighing scales, food bags and hide them somewhere in his work. Again, another tip off to da feds should see him arrested for intent to supply.
You can also hide them at his home but the embarassment of police searching his work premises for narcotics is hilarious within itself.
Even if the CPS throws out any of the above cases, most people are cynical and want to believe it to be true. 'Mud sticks' as the saying goes.