The 40-year-old man, Dharmender Sirohi, suspected the woman Mamta of cheating on him with other men and hatched a plan to kill her, said Chinmoy Biswal, additional DCP-I (South).
On April 8, he took her to Agra on the pretext of a long drive and both of them consumed liquor on the way.
"Once she got intoxicated, he slit her throat with a knife and killed her. He then threw her body in a tunnel along with the knife used in the offence and drove back to Delhi," said the officer.
On April 10, a kidnapping case was registered against unknown persons in Sector 7, Faridabad, Haryana.
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Police received information about a woman whose matrimonial home was in Mehrauli and who had been missing from her parental home in Faridabad.
The informer also said that she had been murdered at an unknown place, said the officer, adding that it was learnt that she was having an extra-marital affair.
Sirohi was arrested from near Khokha Market, Saket on April 12.
Soon their family members got wind of it. Even this did not act as a deterrent and they kept their love affair going, albeit with utmost secrecy.
However, of late, signs of discord appeared when the accused started suspecting that the deceased was showing a lack of interest in him and he found that Mamta was involved with others, said the officer.