Pc Jake Cummings, 25, is charged with two counts of rape, three counts of stalking, three counts of controlling and coercive behaviour and three counts of voyeurism.
The charges relate to three women, one from Hertfordshire, one from Buckinghamshire and one from Dorset, Hertfordshire Police said.
The offences, which are alleged to have occurred between July 2019 and February this year, include Cummings watching one of the alleged victims using security cameras, and detaining another in his car.
Opening his trial at St Albans Crown Court on Tuesday, prosecutor Tom Little KC said the defendant engaged in “extensive controlling, coercive and manipulative behaviour” as he “thought he was above the law”.
The prosecutor said Cummings, from Hemel Hempstead, “behaved in a strikingly similar way” towards each of the complainants.
The court heard that he became a special constable with Dorset Police in 2018 when he lived in Weymouth.
He joined the Metropolitan Police as a constable proper in November 2019 and moved to Aylesbury, Buckinghamshire.
Cummings always had his warrant card on him, even when off duty, and would sometimes “flash it about”, Mr Little said.
The prosecutor said Cummings used phone apps called Life 360 and Team Viewer to track the first complainant and that their combined use gave him a “pincer-type control and knowledge” over her movements.
All three complainants had downloaded Life 360 on their mobile phones, the court heard.
There were just over 5,000 communications between the defendant and the first complainant in a single month, and most of the contact was “very one-sided” from Cummings, Mr Little said.
When the complainant blocked Cummings on Instagram, he set up another account and continued to message her pretending to be somebody else, the prosecutor said.
The complainant saw Cummings driving down the road where she lived, despite not arranging to meet him beforehand.
Mr Little said Cummings insulted the second complainant, who had dyspraxia, and deliberately tried to trip her up in public, which “allowed him to maintain and strengthen his control over her”.
In part of a statement read out by the prosecutor, the complainant said she felt “as if her breathing and blinking were controlled by him”.
The three women, who were aged between 19 and 24 when the alleged offences occurred, did not know each other.
Cummings was originally charged with rape, two counts of stalking, two counts of controlling and coercive behaviour and possession of an offensive weapon in April, which he denied, before further charges were brought in June.
He has since pleaded guilty to two of the three counts of stalking involving two complainants.
The defendant, who appeared wearing a grey tracksuit and spoke only to confirm his identity in court, denies the nine remaining charges.
He has been suspended from his job in the Met’s central west command.
The trial is expected to last three weeks.