1. If Murder was the motive, then accused could have planned when the parents used to be away from house. Particularly mother. 2. Drinking beer and rape attempt is an impossible theory, as servants can not dare such act, when parents are there in the home, and more when they are awake next room. 3. Hemraj calling for Khukri and murder committed by Rajkumar is totally baseless. 4. If these servants have committed the crime they can not hold themselves to normalcy after the investigation started. They would have fled the scene. 5. Behaviour of the parents, prima-facie are suspicious.
The act has been committed by Professional, with the knowledge of parent.
But they under estimated UP Police, who made entry to roof where Hemraj was found. Had Professional Killers conceal Hemraj in a far away place, the case could have booked against Hemraj as Missing person, and closed there itself.
Now these poor servants are made scape-goat by the system, whereas the main culprits are yet to come out.
In no way these servants can work in the household after committing the crime.
Conclusion : The murder has been committed by Dr. Talwar or got it done by Professional. Slip up - They could not destroy Hemraj. If they were successful in doing that, this case would have gone unsolved hunting for Hemraj for years to come.