The evidence points to a specific roommate as being the killer, along with peripheral involvement by other people.
The possibility that a string of child murders, including the murder of Hser Ner Moo, could have been the work of a small group of law enforcement officers has been discussed on another page.
Here are other possibilities.
1) Could Esar Met actually be the killer?
Most of the evidence used by the prosecution to convict him was nonsense.
He also seems to be 99% excluded by the time of death, including the rigor timeline. The body was still in full rigor at 530 am on April 2nd, which was about 40 hours after he left, so that makes it unlikely he is the killer. Several other pieces of evidence probably exclude him also.
But there is evidence that could be seen as needing further investigation.
Notice the slight spot on the right side of his head that may be missing hair. The victim had several hairs clutched in her right hand.
Remember also that during the interview he correctly knew where the shoes were, though it was his second guess.
2) Is it possible he injured the girl severely, as described in the police interview, then his roommates found the body and staged the sex crime?
This possibility arose briefly during the interview, and was dismissed, but it deserves consideration.
If the girl had been severely injured by a fall down the stairs, the roommates would have been hesitant to call police for two reasons,
1) Issues having to do with time card games would have come to light, and more importantly,
2) They might have been accused of the killing.
They were from a refugee camp where there is no effective external justice system, so the main evidence of guilt is almost always proximity to the crime. A body in the apartment while they are there would be proof of their guilt, by their view, unless evidence showed otherwise, evidence such as the body being in somebody else's space.
This scenario explains the rigor timeline, since she could have laid injured for up to 24 hours, unconscious as a result of her asthma plus her injuries.
This would also explain the two kicks to the head.
The strongest evidence against this scenario would be in certain details of how the body and clothing were placed, which would tend to point to one specific roommate and exclude the others.