Reb's blog links to several other news articles on the story that are really illuminating. The initial reports were made by former members who would attend services and noticed the pastor preaching about the "rod" combined with parents removing their children to side rooms and hearing the spankings going on, even the infants.
In one news article the prosecutor is very careful to mention that this is NOT a case of religious freedom, that the Law cannot be broken in the name of God; and I imagine this is why there's such a careful and methodic case being built including the notation of the church's origins and interviewing the former pastor. If these people are going to claim that they are simply being persecuted in the name of their faith, that this other church holds a grudge, or any number of other things the criminal complaint must be clear about who said what and when and why.