Two more cases that highlight the crucial forensic work done by expert witnesses in solving major crimes. This programme reveals how analysis of soil finally brought some justice to the grieving family of murdered woman Becky Godden. Not every piece of evidence that detectives discover will be admissible in court. Even if it identifies a killer. In 2011, police investigating the murder of a Becky Godden in Swindon knew they had the case cracked, but they weren't allowed to present their key evidence at trial. They needed alternative proof. So they turned to an expert witness. The next case explores how digital imaging offers detectives a powerful tool by revealing clues otherwise invisible to the naked eye, making unexpected comparisons between pieces of evidence. That's what happened in this case, when an expert's digital imagery of an unusual-looking bruise led detectives right to the feet of a violent killer. The key to cracking the case? A tiny stone.