In 2372, he traveled to Deep Space 9 where he attempted to sell Tallonian crystals. Constable Odo hoped he could use Regana Tosh to infiltrate the Markalian smuggling ring. However, the operation failed when Worf intervened. Worf was finding it difficult to adjust to being in the command section of Deep Space 9 instead of being in security. Odo was only able to arrest the middle man of the smuggling organization.
Regana Tosh was a known felon and was considered dangerous. He was convicted of trafficking in jewels of sound on stardate 4585.8 and served a three-year sentence at the Kar Zartkaar detention facility. (DS9: "Hippocratic Oath")
The information in the last paragraph of Worf's PADD, which featured information about the criminal from Markalian law enforcement, was barely readable. On that PADD he was identified as Jadwel Tarmak even though the picture clearly showed the alien sitting at the bar (who was later identified as Regana Tosh). It is likely that his name was changed during production and wasn't changed accordingly on the PADD, or that the people working behind the scenes just thought the information on the PADD wouldn't be legible on the TV screen.
Due to a typographical error, the stardate listed would put the beginning of his imprisonment somewhere around the time of TOS Season 2. Rather, it was meant to say stardate 45858, which would mean he finished his sentence sometime during DS9 Season 3.