Criminal Law Questions? Ask a Criminal Lawyer.
if you can interject yourself into the conversation, then you can record it and reveal the contents. but if you are not a party to the conversation, then you need to have permission of at least one of the parties to record.
Wisconsin law only allows taping when a party to the communication is aware it is being done. in other words, you must be a part of the conversation some how or you will be breaking the law
you can also consider bringing in a friend or neighbor while they are discussing this who will then be able to testify what is occurring. at any rate, i suggest you contact the health department and let them know what you heard and suspect so they can get in there and see what is happening