Convinced his former partner was seeing someone else, Greg Scott trashed her home.
He then stole her mobile phone in a bid to confirm his suspicions.
Scott, 21, of Laidlaw Terrace, Hawick, appeared from custody and admitted behaving in a threatening or abusive manner at Melrose Court, Hawick, on October 20, and stealing a mobile phone.
Procurator fiscal Graham Fraser said the accused had been in a relationship with an 18-year-old woman for some two years, but they broke up about a month ago.
“The accused was suspicious that she had started a new relationship and went to a neighbour’s house asking if she knew where the woman was,” he explained.
A short time later, his ex-partner saw the accused, who approached her and warned, ”You’d better not have been with someone else, or I will kill myself.”
Inside the home they previously shared, Scott began knocking things over.
“He knocked a television from its stand and an ashtray was broken,” said Mr Fraser.
The woman began to scream and Scott seized her Blackberry to check who she had been in touch with.
Police found the woman “very distressed”.
“She said her ex-partner had trashed her house and taken her phone,” added Mr Fraser.
Defence solicitor Matt Patrick said when Scott was unable to contact his former partner, he made his way to her address.
“Rumours were flying regarding a new relationship, and he has not handled this as maturely as he should,” explained Mr Patrick.
“She gave him the keys and he let himself in, and then completely lost control and damaged the property inside.
“He took her mobile phone to check it, which unfortunately confirmed his suspicions,” added Mr Patrick.
The solicitor said Scott attended at the police station and made a full admission to police.
“He is not proud of his behaviour, but has not dealt with the break down well,” he concluded.
Sheriff Kevin Drummond told Scott: “This is not the first relationship to break down and it will not be the last.
“Your former partner is perfectly entitled to engage in whatever lifestyle she chooses,” he added.
“You are not a persistent offender, and have spent two nights in custody, but I want to ensure there is no repetition of this.”
Sentence was deferred for nine months, until July 22 next year, for Scott to be of good behaviour.