The masked woman nervously approaches her target, shuffles into position and then unleashes a flurry of lashes -- proving herself as the newest member of the first female flogging squad in Indonesia's Aceh province.
The new recruit initially needed some coaxing to punish the offender -- an unmarried woman caught in a hotel room with a man.
Such behaviour constitutes a morality crime in Aceh, the only region in the world's biggest Muslim-majority nation that imposes Islamic law -- known as Sharia. Those found guilty of breaches are often publicly whipped with a rattan cane.
But despite her reticence, she persevered and delivered her first flogging.
"I think she did a good job. Her technique was nice," Banda Aceh Sharia police chief investigator Zakwan, who uses one name, told AFP.
The controversial punishment enrages rights activists and generates heated media debate, as well as amongst politicians.
Indonesia's president has issued a call for the public floggings to stop but he has little say over what happens in Aceh, a deeply conservative region on Sumatra island.
Unlike the rest of the nation, Aceh follows religious law as part of a 2005 autonomy deal agreed with the central government that ended a decades-long separatist insurgency.
Here, public whipping remains a common punishment for scores of offenders for a range of charges including gambling, adultery, drinking alcohol, and having gay or pre-marital sex.
But the job has always been done by men. Until now.
- 'No mercy' -
More and more women are being charged for morality crimes such as public affection or premarital sex, experts say, as greater internet access and globalisation bring clashes with local cultural and religious norms.
Enforcement too has increased and now Aceh says it's trying to follow Islamic law, which calls for women to whip female perpetrators. This is already what happens in neighbouring Malaysia.
But convincing women to participate has been no easy task, and it's taken years to assemble the first female squad, according to Safriadi, who heads provincial capital Banda Aceh's Sharia Implementation Unit.
Eight women -- all Sharia officers -- agreed to be floggers and were trained in the appropriate technique and advised how to limit injury.
Previously, a dozen men performed all the whippings in the city for an unspecified fee.
For security reasons, Aceh officials declined to let AFP speak with the floggers, who are outfitted in cloth masks and loose fitting brown uniforms to hide their identities.
"We train them to make sure they're physically fit and teach them how to do a proper whipping," Zakwan said.
But the secret for any whipping is getting past the mental hurdle of lashing fellow citizens.
For that, you need to look to God, Zakwan said.
"It's kind of an indoctrination that we give to them so they have a better understanding of their role -- have no mercy for those who violate God's law', he added.
- 'Too lenient' -
Aceh officials insist caning deters crime, with patrols often scouring public places and establishments -- or acting on tip-offs -- to monitor behaviour.
Sharia police in Banda Aceh, a city of some 220,000 people, are on the streets round-the-clock in three shifts.
On a recent patrol, a couple sitting close to each other on the beach escaped with a reprimand.
But a group of men and women spotted at a coffee shop around 3:00 am weren't so lucky and were arrested on suspicion of breaking strict codes about unmarried men and women interacting.
"This shows that we never sleep looking for violations of Sharia (Islamic law)," Safriadi said.
From behind bars, one of the men said that there was nothing romantic happening at the coffee shop.
"We don't even know the women and were sitting at different tables," he told AFP.
The women were later released with a reprimand as were the men, but police said the trio may be charged for a new offence, after it was determined they were gay.
Same-sex relations can earn residents a whipping in front of jeering crowds, which can number in the hundreds.
"Sharia in Aceh is still lenient," said resident Saiful Tengkuh.
"Aceh needs harsher punishments like stoning, not just whipping. Someone committing adultery should be stoned 100 times," he added.
- 'Don't do it again' -
Aceh, home to about 5 million people, once mulled beheading for serious crimes, but the central government ruled it out.
This summer, it made headlines over a fatwa, or religious edict, against online game PlayerUnknown's Battlegrounds (PUBG) and opposing a national women's football league because it didn't have a stadium where only female players, match officials and spectators would be present.
But whipping is often what gets Aceh in the news -- unwanted attention local officials say is Islamophobic.
Advocates say many people caught breaking religious law choose whipping as an efficient, if painful, way to avoid a stiff jail term.
But this rough justice can take a toll.
Floggings can be so severe that people pass out or are hospitalised, with the most serious crimes -- including gay sex and having a relations with a minor -- earning as many as 150 lashes.
Many offenders have fled the area out of shame or because customers deserted their businesses. Few are keen to discuss their experience.
For women, arrest for even a minor violation can lead to victimisation, including sexual harassment and rape during arrest, according to research by the Network for Civil Society Concerned with Sharia.
Reporting these assaults without proof can even open up victims to flogging for making a false accusation, it added.
Human Rights Watch and Amnesty International have condemned such punishments as "barbaric", "inhumane", and tantamount to torture.
But Aceh officials insist they're "far more lenient" than ultra-conservative Saudi Arabia and some other Muslim nations.
"We're not aiming to hurt people by whipping them," Safriadi said.
"The most important thing is the shaming effect on violators and spectators so they don't do it again."