He should`ve tried hard to go down the supply chain himself...
...not just Nokia > ... > ... > ... > ... > Mines.
Bribe some people, stalk some people, investigate some people, figure out who the missing links are.
That's exactly the problem with the film. When he tried to heap all the blame on Nokia it was totally unfair.
I'd of liked to know whether these materials are used in hard drives, processors or transmitters. Just so I could have a slightly bigger picture of how big a player Nokia is in the purchasing market. If he'd figured out the 5 or 10 biggest purchasers, he might of been able to shame some more than others to get a level of competition in stopping it.
It would of been good to know if the people who could tell the source of the minerals had been able to do that for a long time or if it was a recent development. Were the purchasers ignoring them or had they just not realized this technique existed. (He might of covered this one. I can't remember).