The evidence assessed by forensic experts — from hair samples to fingerprints — routinely plays a decisive role in prosecutions across the country. In popular television shows like CSI, their work is presented as slick, sophisticated and infallible.

But FRONTLINE producers Lowell Bergman and Andres Cediel uncovered a different reality in which the “science” of forensics is — in many cases — not based on science at all, and the credentials some forensic examiners offer to prove their expertise may not mean what we think they do.

Just how widespread are the shortcomings? Where is the oversight? Who is pushing for reform? What might an improved system look like?

We’ve asked Lowell and Andres to join us for a live chat to discuss these questions, and take yours.

They’ll be joined by guest questioner Jeffrey Toobin, a lawyer, author, veteran staff writer for The New Yorker and CNN’s senior legal analyst. His most recent book is The Nine: Inside the Secret World of the Supreme Court. You can follow him on Twitter: @JeffreyToobin.

You can leave a question in the chat window below, and come by at 1 p.m. ET  on Thurs. April 19, to join the live discussion.