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Profiles in Justice: Assistant District Attorney Katherine Ernst

Assistant District Attorney Katherine Ernst’s journey to becoming a prosecutor in the Philadelphia District Attorney’s Office Federal Habeus Unit earlier this year started with a rather unlikely subject: Horses.

“The actual reason I decided to go to law school was that my father was a lawyer, and he had this case that was before the Pennsylvania Horse Racing Commission. And I went with him to a hearing one summer, and right before the hearing, my father’s client came up to him and said: ‘Alan, the fix is in! They’ve gotten to our witnesses!’ And I thought that just seemed so exciting that I wanted to be a lawyer.”

After graduating from Loyola University New Orleans, College of Law in 2007, Ernst went into criminal law for a very brief period in 2008 before moving into civil law for approximately a decade. In 2017, however, she made the decision to return to criminal law and joined the Montgomery County Public Defender’s Office with a desire to do trial work once again. But thanks to her excellent writing skills, she found that she was very well-suited to appellate work instead, and flourished in that section.

“There was so much good work to be done in state court appeals. And I had a real knack for it, so I basically decided to stay and do that instead of trial work.”

After winning numerous appeals, some precedent-setting–including Commonwealth v. Talley, which established a heightened evidentiary requirement necessary to deny bail to defendants–while arguing before Superior, Commonwealth, and even Pennsylvania Supreme courts, Ernst continued her appellate path. At Wiseman Schwartz, she eventually took up federal habeas cases, which involve appellants who have exhausted their state-level claims after 10 years or so, if not longer.

“I found it to be a very interesting area of law. All of the cases that we have are very old, and reflect a time when the search for justice wasn’t as strong as it is today. There’s a lot of good that you can do in federal habeas,” she says.

While at Wiseman Schwartz, she saw the work being done by the DAO’s Federal Habeas Unit and its Supervisor, Matthew Stiegler. She was very impressed with the approach the DAO took to pursuing justice – particularly after her experience with other prosecutors while serving at the Montgomery County Public Defender’s Office.

“I really saw that it was a search for justice. You know, if someone was guilty and they didn’t have any viable claims, well, that’s obviously one thing. But if there was significant evidence of Constitutional violations, and that the person very well may not have committed the crime, then the Philadelphia District Attorney’s Office takes that very seriously.”

Ernst currently lives in Manayunk with her husband and two children. When she’s not pursuing justice in federal court, she advocates for women’s disability issues, including health diagnosis disparities and sexism within the treatment community, after experiencing these problems first-hand after a diagnosis. Until last year, she blogged extensively about these issues, and has been featured in Prevention Magazine and on

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