Since childhood, Jason English has been familiar with the law due to growing up with a father who was an attorney and owner of a personal injury law firm in Tarrant County, Texas. This early experience influenced English's decision to become an attorney himself. After graduating from Texas A&M, he earned his law degree from St. Mary's University School of Law. Upon graduation, he joined his father's law firm, practicing personal injury, wills and probate, and family law. To obtain trial experience, at his father's advice, English joined the District Attorney's Office.

He was an Assistant District Attorney with the Travis County District Attorney's Office in Austin, Texas from 2007 to 2017. The Travis County District Attorney's Office has jurisdiction over felony offenses. English was a prosecutor in Texas from 2002 to 2017, working at the Cameron County Criminal District Attorney's Office in Brownsville, Texas and the Hays County District Attorney's Office in San Marcos, Texas.

Initially, English worked in a variety of courts, handling all types of violent crimes, drug crimes, and DWIs. He was assigned to the Special Prosecution Division's Public Integrity Unit during his time with the Travis County D.A.'s Office. This special unit was responsible for prosecuting white-collar crimes committed against state agencies or state officials. He also worked as the liaison between the D.A.'s Office, the Austin Police Department, and the community when he was the Strategic Prosecution Unit's Community Prosecutor. In this position, he addressed special issues or top offenders that had an impact on the community. During this period, English counseled the Austin Police Department about sting operations and felony cases. Implementation of a Drug Market Initiative following the High Point, North Carolina model, an enhanced prosecution initiative, was just one of the initiatives included in his work.

During his service as a prosecutor, English had also been responsible for various diversion programs for the Travis County D.A.'s Office, such as the Mental Health Docket and the Veterans Court, which he specifically handled. After being a prosecutor for 15 years, English returned to his roots. His practice now involves personal injury, will and probate cases, and criminal defense. Taking his father's wise advice early in his legal career has given him valuable trial experience prosecuting criminal cases. This practical experience now benefits those he defends against criminal prosecution.