We need information about the parents and their friends, to know who they are, what they do, if they have problems in their country, if the children were victims of abuse, if the family, neighbours, friends could have noticed any suspicious behaviour, what are their jobs, if they work full-time, etc. Is any member of their family depressed or suffered from depression in the past? Do the couple maintain good relationships? Are they implicated in serious litigation? Do they have enemies? For what reason?
Now that is pure Stasi - interview anyone who knows the accused and hope at least one of them, fearful of contamination and therefore open to 'reason', will then provide the incriminating evidence required to convict. The whole situation is engineered to the premise 'guilty unless the accused can prove otherwise' never 'innocent until proven guilty.' One would hope that such practices were a thing of the past - the totalitarian left or right wing regimes having been removed, but even when a country becomes a democracy such ideologies are still in force especially in the police and army. It takes time for this attitude to change.