Vincent "Vince" Walter Korsak is a homicide sergeant detective at the Boston Police Department. His badge number is 987.
Korsak once served as a marine in Vietnam. This, however, ruined his marriage with Dana, his first wife, which lasted three weeks before he was sent off to Vietnam. The long-distance marriage went on for almost a year until Dana met someone new and left Korsak.
During the Irish crime war days, those of Whitey Bulger's and the Winter Hill gang, Korsak was a rookie, and for a beginner had already seen things that still seem to bother him.
Vince Korsak has apparently been married to three women, the third of whom was Melody Patterson, his "last and best" and the ex-"wife that got away". He raised her son, Josh, for ten years as his own before Korsak started to get too sucked into his job as a detective. Josh's biological father then convinces Melody to get back with him and move to Florida. Melody then divorces Korsak and takes Josh away from him, letting him believe that Korsak was no longer interested in him, leaving Korsak heartbroken since, in reality, it is quite the opposite as Korsak genuinely loves Josh like his own son.
While still working as the partner of Jane Rizzoli, they end up handling the case of "the Surgeon" Charles Hoyt, a necrophiliac serial killer. Jane is then held captive by Hoyt and, just when she was just about to be added to Hoyt's list of several victims, Korsak storms in and saves her from Hoyt.
Vincent theorizes that the reason Jane no longer wants to be partnered with him is because he reminds her of that day he saved her from Hoyt and that she is "broken" and fears she will never be able to repay him.
Although the two maintain a close bond after years of working together, Korsak still wants to be partners with Jane, which is a feeling not shared by Jane. Because of this, Korsak was often hostile towards Barry Frost, Jane's new partner. Eventually though, the two begin to bond while working cases together with and for Jane. Although the two constantly bickered at first, especially when it comes to the skill and capability of the other to work with Jane, their relationship has slowly become more civil and amicable.
Some time before "We Don't Need Another Hero" during Jane's leave, Korsak has been promoted to the rank of Sergeant of the precinct.
Although still constantly bickering with Frost in occasion, they are no longer hostile towards each other now that they are in a three-way partnership with Jane. He has even shown concern towards him, particularly when he saw that the arrival of Frost's father seemed to have bothered his new partner. He asks Frost if his father has ever told him that he was great at his job. When he finds out that the admiral hasn't yet, he goes on and tells Frost that he is a great detective.
Vincent is evidently a passionate animal lover, although not passionate enough to give up meat. He will drop whatever he is doing on a moment's notice to rescue an animal. He also apparently enjoys watching videos of dogs on the Internet.
Korsak is Jane Rizzoli's former/original partner and unofficial mentor. The two maintain a close bond after years of working together, but Korsak is clearly bothered that he is no longer partnered with Jane. He seems to care for her like a daughter and is nearly as protective of her as Angela is. It is revealed in the series pilot that he saved her life from Hoyt. Korsak is the the 'Father' figure in the series, not only to Jane, but also it Frost and Maura, who both have less then active fathers.
|“|| F: You don't have to... be my dad.|
K: I'm not old enough to be your dad.
–Frost & Korsak, Sailor Man
In the first season, Korsak and Frost generally do not to get along. Over time, however, with Jane's urging, their relationship slowly improved. Korask is a positive parental influence to Frost, their relationship is similar to Jane and Angela's.