David Leonard had served two jail sentences before being hired as the city’s parks manager last year, but in accordance with its usual practice regarding the hiring of contractors, the city hadn’t checked his background. Leonard is now the subject of a police probe in which he is charged with stealing $43,000 from the city’s Belleville Improvement Society, a nonprofit that oversees the city’s Atkinson Common park. After committing those alleged thefts, Leonard bid on — and won — a job to maintain Newburyport’s parks. He was fired earlier this year, when the city discovered he was being investigated for the Belleville thefts. According to Mayor Donna Holaday, his criminal record was not checked because Leonard was a contractor and not a city employee, he was not subjected to a Criminal Offender Record Information check. Holaday said there was never an issue with Leonard’s work until February, when the city learned he inappropriately failed to pay a subcontractor.