Already facing flak for its investigations in Aarushi double murder case, the CBI has quietly conducted a narco analysis and brain mapping tests on the parents of the 14-year-old girl recently, a scientific procedure to which it was opposed in July last year.

CBI, which is maintaining a studied silence about the probe in the case after coming under attack as all those arrested walked out on bail, asked Aarushi's parents - Rajesh and Nupur - to appear for these two tests, agency sources said on Thursday.