I'm not sure why people automatically assume that DY, TY, and KH are only being called to testify to suspicion or gut instinct.
I think it is more likely that their purpose there is to give testimony about things related to custody... like who had him during the summers, what they did, where they went... things of that nature. I'm also betting that KH recounted the last morning he saw Kyron. I think they were probably giving the backdrop of his "blended family" and the way it functioned.
The prosecutor asks the questions. I'm sure he wanted the jurors to have a basic understanding of the family dynamics... particularly if one member of the blended family is being investigated.
I understand that many people here wish to not be part of the "witch hunt." I don't want to be part of that either. Desiree doesn't know what happened to her son, but she has suspicions... I'm not sure how that correlated to the police only having the same "gut feeling." We don't know what is going on, of course, because in Oregon the public information laws aren't like they are in Florida. But to assume that the government is trying to railroad Terri Horman 'because they got nothin' is the same presumptuous and damaging leap as trying to tie Terri to the stake. The police aren't in the business of just wasting public money, time, and resources... at least not with this deficit. Instead of analyzing and dissecting information, seems people just end up picking at each other over what sources are trustworthy.
Its as if this has already become the JonBenet forums, any information that doesn't fit a particular side will be attacked, scrutinized and even discredited, with no real purpose of justice, other than continuing to validate a particular side of the fence.
So they were called before the grand jury. They each probably have unique unbiased information about Kyron's daily life, and who had access to him. If they are asked about their subjective opinions, I'm sure they will offer them up, but to assume that all they can offer is eye rolling disgust of the evil step mother... is probably not true. Forgive me