Teegar Lawless was an unpleasant man even before he served two tours in Vietnam. He comes home in 1972, assuming he can simply leave the experience behind, but he becomes even more unbalanced, violent and alienated than ever. He suffers many typical symptoms of Post-Traumatic Stress Disorder - sleeplessness, nightmares, extreme irritability and emotional disconnection from his family - and he begins drinking heavily to deal with this.
During a night of blackout drinking, he discovers that an outstanding gambling debt from before his service has swelled to $15,000, and that he has two weeks to pay up or the underground casino boss Barber will have Teeg's sons, Tracy and Ricky, killed.
Teeg and his friend Willy have barely made a dent in that sum after a week of small-time robberies when Hamsunn, the owner of the Undertow, introduces him to Danica Briggs and offers them a shot at robbing some gangsters (supposedly Mexicans.) Danica hooks up with Teeg, then convinces him to cheat Hamsunn and flee the city with her once his debt is paid off.
The job itself goes smoothly, but when Teeg tries to pay his debt, Barber refuses the money. Teeg and Willy had robbed an operation run by Sebastian Hyde, son of the underworld boss Walter Hyde. Teeg returns his share of the money, but Sebastian insists he must do more to avoid dire consequences. He beats Hamsunn to death, shoots Willy and cuts Danica's throat, leaving her body in an alley. Sebastian then gets Barber to reduce Teeg's debt and allow him to pay it off slower, so he can remain in town and do more work for the Hydes.
Last Of The Innocent
In 1982, Teeg is working for Sebastian Hyde and crosses the path of Riley Richards, first to remind him of his outstanding gambling debts and later to tell him about the private investigator after him. Richards determines that his father-in-law hired the PI to connect him to the murder of his wife, and calls Teeg to ask a favor - arrange for the man accused of the wife's murder to die in prison.
In 1989, Tommy Patterson goes to prison for killing Teeg, but in Criminal #5 it's implied that Tommy's son Leo actually killed him. A conversation in Criminal #7 confirms that Leo was the killer (and that Teeg's son Tracy knew.)
Other mentions and flashbacks
Teeg's first on-panel appearance is Criminal #7, in a flashback to Tracy Lawless's childhood. Teeg takes his sons to a rooftop to shoot pigeons for target practice. Tracy is unfazed, but his younger brother Ricky is upset by the first bird's death, which infuriates Teeg.
In Criminal #9 Tracy visits the graveyard where his mother, father and brother are buried. Teeg's gravestone reads "1942-1989". Tracy recalls his father taking him on the run in 1979, robbing gas stations and teaching the boy how to steal cars, while Ricky stayed home and watched their mother die of cancer.