Stickler was a regular at Trucy Wright's magic shows at the Wonder Bar, and he was fascinated by the "Magic Panties" act, in which she pulled large objects out of a pair of bloomers. In vain attempts to quench his curiosity, he began to steal panties from other people. One day, he stole Trucy Wright's panties, but she chased after him. He was forced to hide behind a car, stuffing the panties into an exhaust pipe. He later stole a pair belonging to Plum Kitaki, but came across two people in People Park, Wocky Kitaki and Pal Meraktis, the former threatening the latter with a weapon. Stickler threw the panties away and then shouted at Wocky to stop, causing Meraktis to turn his head and get shot in his right temple. Wocky ran off, and Stickler ran to a nearby phone to call the police. Kitaki was later tried for the murder.
When Stickler was called to court as a witness to the murder, he lied about the location in which he was standing to hide his identity as the mysterious "panty-snatcher" who had stolen the panties of Plum and Wright. However, Wocky's lawyer Apollo Justice saw through his lie by reading his tell; he would play with the corner of a page of his book when talking about the moment of the murder. Thus, Justice simultaneously solved the mystery of the panty-snatcher and cast doubt on Wocky's guilt based on the location of the victim's gunshot wound.
Stickler was subsequently arrested on suspicion of petty theft, and held in the detention center to be questioned about his own crimes and to corroborate Wocky's account of events. It would appear that no severe charges were brought against Stickler, as he would later be seen outside the detention center, although his already-questionable reputation among his fellow students greatly suffered and he picked up a few new derisive nicknames from his peers for his panty-snatching.
Stickler is very proud and conceited. He has a tendency to ramble on and on about details (usually of a scientific nature) when given the opportunity to go on a tangent. As someone priding himself on his education, he demonstrates his overlarge vocabulary as often as he can, speaks very quickly, and never uses one word when several will suffice. Those with similar habits are Redd White, Richard Wellington and Wendy Oldbag (although White just uses overly-elaborate words and does not speak in a very fast manner like Wellington or Oldbag do).
Stickler seems to be the subject of ridicule for his peers; he has been given names such as "Wesley Stinkler" and "Wesley Stickyhands". He later gained the nickname "Wesley Sicko", probably as reference to his panty-snatching (though Stickler misunderstood its meaning as an honorable one).
His Japanese surname, "Kawadzu" (河津), is close to the word "kawazu" meaning "frog". This may be a reference to the old Chinese idiom "a frog at the bottom of a well", meaning that he is oblivious to the workings of the outside world.
"Wesley" may be a play on "weaselly", meaning "devious", "misleading" or "sneaky". This could be a reference to his panty-snatching habit.
A "stickler" is a person who is extremely fussy or particular, and insists on precision or correctness.
"Tatillon" is the French equivalent of a "stickler".
He was originally intended to be a biseinen ("pretty man") and traces of this are still very noticeable in his character design; Apollo Justice's comment to Trucy Wright that Stickler would "make a great 'lovely assistant'" may be a reference to this.