In 2010, fire expert Gerald Hurst talked with PBS' Frontline about arson science and the case of Cameron Todd Willingham, who received the death sentence in 2004. It can be difficult to prove arson in a case, Hurst said. It is still fair to try to convince a jury without scientific evidence of arson, he added. A prosecutor could use evidence that the accused was motivated to kill the people who died in the fire, for example. However, investigators need to recognize when they just can't tell, which can often happen, Lentini told 60 Minutes.