or even criminal negligence, since their seed contaminated your crop, then the contamination was used in a shakedown.
Trespassing in Indiana can be fined up to $1000 and 6 month jail sentence. Each of these seeds are "their" property. Lets say that a contaminated field is 500,000 seeds. $1000 per seed is $500 Million.
Of course, if Monsanto abandons their "property", or lays no claim to it, there wouldn't be a judgement on trespassing.