The plan is simple but the results always startling: walking into a diagnostic centre posing as a couple and seeking to determine the sex of the baby in the womb.
Once the foetus is determined to be a girl, ask the doctor in attendance if the pregnancy could be aborted. And if the doctor agrees to carry out the procedure, call the police and get the medical practitioner arrested.
For more than a decade now, the decoy couples have struck terror in the hearts of doctors on the lookout for making quick bucks by carrying out female foeticide – the illegal procedure of thwarting the birth of girl child, considered still by many Indian families to be a curse.
As fear of the entrapment has grown, so has the fame of Rajen Choudhary, the 49-year-old crusader from the western Indian state of Rajasthan, earning him the epithet "Friend of the Unborn".
The stings carried out against doctors have been his brainchild. In doing so, he has won praise and awards and constantly braved threats to his life alongside.
"To save the girl child is my mission," insists Choudhary. Agrees Lad Kumari Jain, the chairperson of the Rajasthan State Commission for Women: "He has been an asset in the fight against female foeticide. Whenever we need him, he is there to help."
With one of the most skewed sex ratios in the country, it had been apparent for some years now that Rajasthan had become a haven for sex-selective abortions.
The practice is illegal in India, but it continues to thrive nevertheless.
Choudhary woke up to the menace in 2001 after the official census report threw up alarming facts: the ratio of girls in Rajasthan had dropped from 916 in 1991 to just 909 per 1000 boys.
"It was then I decided to fight for the right of the girl child," says Choudhary.
It has been an arduous battle since then, with his adversaries including greedy medical practitioners and a slew of ultrasonography centres run by influential people.
The cause for his campaign remains dire: Some 1,800 ultrasonography machines are reported to be in operation across the state, and the male-female sex ratio is ever widening.
It has fallen further and the 2011 census figure puts the ratio of girls at 8.8, against the national average of 914 girls per 1000 boys.
The declining ratio of girls is attributed to illegal abortions: Reports suggest that out of one million foetuses aborted annually in India, some one-hundred thousand are in Rajasthan alone.
Alarmed by deteriorating situation, Choudhury has been resorting to desperate measures.
He set up the Shikshit Rojgar Kendra Prabhandhak Samitti (SRKPS), an NGO dedicated to save the girl child, with his team raiding doctor's chambers at regular intervals.
"He provides us specific information regarding sex determination being done in clinics. When we need, he also provides us with a team comprising a pregnant lady and other important members to conduct the decoy operation," confirms sub-divisional magistrate of (SDM), Jaipur, Alka Bisnoi.
|School girls pose with placards during a protest march against female foeticide [File: AFP]
Among those Choudhary's team has ensnared so far include an important office-bearer of the local chapter of the Indian Medical Association. The doctor caught in the illegal act had ironically lent his support to the campaign against sex-determination tests.
The Rajasthan government has a policy of giving cash rewards (up to $1500) to informers who help in uncovering such malpractice. Choudhary has been rewarded by several district administrations within the province so far.
But together with rewards have come quick retribution from those who find themselves at the receiving end.
The owner of a nursing home in the town of Sikar has filed a court case against him, accusing Choudhary of "fixing" him after his extortion attempts failed.
Another doctor, whose wife's clinic was raided, is also unsparing in his criticism of Choudhary. "He had first demanded Rs 21,000 ($332) as a bribe and when we did not fulfil his demands, he implicated us in a false case," the doctor claimed.
Choudhary's mission is undoubtedly lined with dangers and his wife, Durga, often is forced to spend sleepless nights.
"We often live in fear, as he keeps getting death threats. We have sleepless nights when he is on the mission of conducting a decoy operation, we do not sleep till he returns home," she says.
But unmindful of the threats to his life, Choudhary carries on with his fight to save life in the womb.
Even his daughter Jyoti has made up her mind to join the fight.
"As soon as I complete my education, I will devote my time to save the girl child," she says.
After all, any help is not too small when the fight is against illegal abortions born out of social prejudices against the girl child.
Follow Shahnawaz Akhtar on Twitter: @ScribeShah
This feature is a part of our ongoing special India coverage. To read more stories click here.