Wayne Bamford secretly planted two listening devices in Joanna Dawson's home and listened in to one of them more than 1,600 times over the course of 15 days.
-> Woman seriously sexually assaulted on her way to work this morningA court heard Miss Dawson found the devices after going to a 'spy shop' in Leeds and asking for advice when she suspected Bamford was carrying out surveillance on her.
Bradford Crown Court heard Miss Dawson found what appeared to be an adapter plugged in to a socket behind a cabinet in her bedroom.
Miss Dawson took it to the shop where a member of staff took it apart with a screwdriver.
The device contained wires and a sim card.
Anthony Moore, prosecuting, said it was examined by police experts who confirmed the device could be used to obtain a "live audio feed" by calling the sim card number from a mobile phone.
-> Police helicopter and multiple officers called to reports of man with two knives in Leeds streetBamford was arrested and questioned about the device on March 1 last year.
Mr Moore said Miss Dawson found another listening device plugged into the socket behind a television in her bedroom on March 16.
It was discovered that phones attributed to Bamford had made over 1,600 calls to the device during the period since his arrest.
Garage owner Bamford, of Wakefield Road, Gildersome, Leeds, pleaded guilty to an offence of stalking, causing serious alarm or distress.
A hearing took place today to determine the facts of the case as Bamford continued to deny responsibility for the second listening device.
Miss Dawson gave evidence in which she described how she became suspicious after Bamford had told her he had installed a listening device on the outside of her house.
The mum said she became concerned after arranging for a locksmith to change the locks on her home.
Soon after she received a text message from Bamford which read: "There is no need to change your locks."
She said she began to worry for her safety and the safety of her son who also lived at the house.
Miss Dawson said she began a relationship with Bamford in May 2016 and they set up a business together six months later in November.
She told the court the relationship broke down the following January.
-> Dad crashed car and left injured son behind in wreck on Yorkshrie roadShe said: "I just wanted him to leave me alone and didn't want him to be prosecuted.
"At that time, I didn't know how serious his behaviour towards me would get. It's when his behaviour escalated.
"I thought he would stop when he originally got arrested but it didn't, it got worse."
Bamford gave evidence where he continued to deny placing the second device.
He claimed Miss Dawson had "hacked" his mobile phone and then used his number to contact the device in order to get him into trouble.
Bamford claimed Miss Dawson had known about the first device and had asked him to help her "stalk" her ex-partner.
Recorder Anthony Hawks rejected Bamford's account.
He said: "I find the complainant entirely plausible.
"I find the defendant evasive and dishonest. I totally reject his account that the complainant was responsible for placing the device there herself."
He continued: "I find that a ridiculous suggestion."
The court heard Bamford was jailed for 30 months in 2015 after being convicted of money laundering and possession of cannabis with intent to supply.
Recorder Hawks said he wanted a probation report and a psychiatric report to be obtained before sentencing Bamford.
Bamford was granted bail until October 19 but was told to expect a substantial prison sentence.
Recorder Hawks added: "I am very concerned about the risk that you may present to people because, from what I have heard from you and your ex-partner, you were prepared to engage in a highly sophisticated way to stalk that woman.
"This offending was serious and hyper-sinister."
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