According to the girl, she had intercourse with the boy only after finally giving in to his constant requests to sleep with him, the local Skånska Dagbladet newspaper reported.
The affair came to light in June of this year after the girl's mother found numerous sexually-charged text messages on her daughter's mobile phone.
In one message, the 17-year-old threatened to tell the 13-year-old's parents that the two had slept together if she didn't agree to have sex with him again.
When confronted by her parents about the matter, the girl admitted she had slept with the older boy, prompting her mother to report the incident to police.
According to Swedish law, sex with anyone under the age of 15 is considered child rape, regardless of whether there was any threats or violence associated with the incident.
As evidence that that 17-year-old convinced the girl to have sex with him, prosecutor Åsa Okmark cited intensive text message and computer correspondence that took place “24/7”.
In the span of one week in early June, the two exchanged 350 text messages with one another, with the bulk of the exchange consisting of the boy inquiring if the girl wanted to have sex with him.
The 17-year-old has admitted he knew the girl was only 13-years-old when they had intercourse in the enclosed porch at the girl's home earlier in the spring.
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A friend of the 13-year-old has also testified in the investigation that the 17-year-old tried to persuade the girl to have sex with him.