The actor's car met with an accident in suburban Bandra on September 28, 2002, killing one person and injuring four.
A chemical analyst on Thursday deposed before the sessions court in Mumbai, which is hearing the 2002 hit-and-run case allegedly involving Salman Khan, that he had received a vial purportedly containing 6 ml blood of the Bollywood actor but found it had only 4 ml of the sample.
The blood sample of the actor, who was allegedly drunk when he rammed his SUV onto a pavement, killing one person, had been sent for chemical analysis after the incident.
Replying to a question by Salman Khan's lawyer Srikant Shivade, Balashankar, the analyst, said he was not aware where the 2 ml of the sample blood was.
Mr Balshankar had earlier told the court the sample had 62 mg of alcohol, double the permissible limit. A person who consumes alcohol would normally have 30 mg per 100 ml but it may increase by 40 per cent if the person is on medication.
To another question, the analyst said the sample bottle had a label which read 'Salman Khan' and not 'Salman Salim Khan' as put by police in the court case papers.
Advocate Shivade apparently put the question to show that the blood sample could have belonged to somebody else.
To a question about shortfall in the sample, the witness said such things had happened earlier too, but though it was his duty to inform the authorities about it, he did not.
Mr Balshankar also admitted there was no proof to establish that the bottle of sample had come to him and he had verified it; there was also no evidence to show that there was preservative in the sample (a point made earlier by the defence to show that without preservative, blood test would not be reliable).
The cross examination would continue on Friday.
The prosecution had examined the analyst to establish that Mr Khan had had liquor before his car met with an accident in suburban Bandra on September 28, 2002, killing one person and injuring four. He has denied that he was at the wheel.