Former deputy public prosecutor Spencer Gwee was found guilty of having sex with an underage prostitute on Friday.
The 61-year-old lawyer was convicted of one charge of having paid a 16-year-old Vietnamese prostitute $300 for sex at the Four Chain View Hotel in Geylang on the evening of July 19, 2011.
Judge Toh Yung Cheong said the prosecution had proven its case beyond reasonable doubt.
In his written grounds, Judge Toh addressed several key areas of Gwee's defence, including his claim that he did not speak Vietnamese and never had a conversation with the teenager - even though there were records of SMS messages exchanged between them.
"The communication between (the girl) and the accused was more or less limited to requesting sexual intercourse; (she) was not claiming that the accused recited the Iliad or the Odyssey," said Judge Toh.
The judge noted wryly, however, that Gwee "apparently understood" some Russian.
This was referring to the second tranche of his trial in May when Gwee told the court that the investigating officer for his case "was conferring with his apparatchiks for some 45 minutes" when police held him for questioning.
"It was not out of the realm of possibility that the accused may have learnt a few Vietnamese phrases from his frequent visits to Four Chain View Hotel, pubs in Geylang, as well as his trips to Vietnam," wrote the judge.
The judge also addressed Gwee's alibi that he had been discussing business with a client at a Geylang coffee shop around the time the offence occurred.
The client, engineer Arthur Chew, had testified that he was with Gwee on the night of July 19 until about 11.50pm - yet hotel records showed Gwee had checked in at 11.41pm.
"There was a significant likelihood that (the client) was mistaken about the date or time he met the accused," added Judge Toh.
"(And) even though (his) evidence would have been critical, his existence was never mentioned to the police during investigations by the accused."
Instead, the testimony of the defence witness was contradicted by "objective, independent evidence" from the hotel, including oral testimony from three employees and records that placed Gwee at the hotel at the time of the crime.
Judge Toh also dismissed Gwee's theory that the investigating officer was biased and had targeted him especially.
He had argued that his legal career had made him an "important" catch for the police, but this claim was branded "largely speculative and of little relevance" by Judge Toh.
One of Gwee's lawyers, Mr Sunil Sudheesan, said his client will wait until after sentencing - which is due to take place next Friday - before deciding whether to appeal.