It's the Pakistan high courts which refused the voice sample and not the government.Contrary to this India refused the Pakistan investigation from cross examining Kasab in India, why is that.
"The Islamabad High Court on Monday dismissed the petition.
In 2011 and 2015, the issue of obtaining voice samples of Lakhvi had been dismissed by the trial court on the grounds that “no such law exists that allows obtaining of voice sample of an accused”.
The prosecution’s petition said the Indian intelligence agencies had intercepted communication between the suspects and the terrorists in connection with the Mumbai attack in 2008.
In the recorded intercepts, the suspects are alleged to be instructing the terrorists.
The prosecution lawyers had argued that the samples were essential for concluding the investigation of this high profile case.
The trial court had also rejected another petition of the prosecution requesting the court to declare Ajmal Kasab and Faheem Ansari absconders in order to meet legal formalities."