A very sad case indeed, but under what legislation were they prosecuted? There is one comment quoted in the article which states "It's frustrating for us, that the legislation does not allow for the penalty to be proportionate to the offence" which to me suggests they were possibly prosecuted under the wrong law or that the law needs to be amended to allow different penalties. AS for the fire detector not having a battery, how common is that in rented accomodation and how would the landlord know, there are very few inspections of rented homes carried out even by local authorities and housing associations.