Highly-placed sources in the agency said the first post- mortem was conducted at night, which is usually against laid down procedures. Post-mortem is not conducted after sunset except in an exceptional emergency cases.
Ahead of exhuming, CBI will constitute a medical board after which the agency will move a local court for a direction for exhuming the bodies of the two girls for a fresh postmortem.
The move comes after the autopsy report of the state government was only suggestive of rape without conclusively proving it.
The postmortem was conducted by a lady doctor who had no prior experience of it, said the sources.
The two cousins, aged 14 and 15, went missing from their house on the night of May 27 and their bodies were found hanging from a tree in the village in Ushait area the next day. The incident had sparked a nationwide outrage.
Meanwhile, CBI continued the polygraph test of the fathers of the victims at the Central Forensic Science Laboratory.
The sources said a number of questions put to the fathers and an eyewitnesses regarding the sequence of events on the night when the girls went missing, mobile phones of the girls, first time when parents came to know about the incident but the answers not clear.
CBI sources said four persons--fathers of two victims, a relative of the family and an eye witness--have been brought here for lie-detector test as the agency is not convinced with the statements given by them.
The sources said the chain of events given by the eye-witness has many loopholes which need to clarified before reaching any conclusion. They said the statement also lacks consistency.
The sources said CBI has taken three days' time from the court in Badaun to subject these four persons to polygraph or lie-detector test but if the procedure is completed earlier, then they may be allowed to go.
CBI sources said they are not doubting the claims made by the families of the victims but in order to develop a flawless case the agency needs to test the veracity of their statements.
Director General of Uttar Pradesh Police A L Banerjee had also raised questions about the incident. He had claimed the rape of one of the victims was not confirmed while suggesting that property could be one of the motives behind the crime.
The lie-detector test, which is based on the premise that certain parameters of the body fluctuate when a person is lying, measures these parameters of the person undergoing the test and presents to the investigators a graph which shows variation when a particular question is asked.
