True. However, in Canada, evidence is not released to the public before trial.Just because the police have said he was cleared doesn't mean that is true. They say a lot of things as a means to protect the investigation. They want the suspect to think they are in the clear so they slip up.
Here, we have quite a bit of evidence released to Unsolved Mysteries, including crime scene photos. Police have ruled out every potential suspect, every criminal possibility, and they want to know whether anyone knows something, no matter how small, that could move the investigation in a different direction from 'accident'. Unsolved Mysteries has resolved murders.
Police rarely declare that someone known to the victim is ruled out. Husbands are rarely ruled out. In this case, the husband has been officially ruled out after an extensive police investigation. His sister is also officially ruled out.
Several months after Amanda's death, the husband gave his sister's information to police. He wondered whether his sister was murderously angry after Amanda reported her young child to social services. The child was put into foster care, and the husband's sister was angry.
The husband's sister was a drug addict who was unable to raise a child, and she might have verbalized her frustrations to other drug users, who may have thought they were doing a good deed by pushing Amanda down the stairs. That's possible.