BBC Two's 'best' true crime documentary is set to return to television screens tonight with a spine-chilling investigation.

Immersing viewers in serious criminal cases, Forensics: The Real CSI follows West Midlands Police as they launch major investigations. In a frantic race against time, disturbing truths are unearthed as detectives pursue justice.

Hailed as essential viewing for fans of 24 Hours in Police Custody and Catching a Killer, the documentary series centres on forensics teams who frequently face little to no evidence, as they piece together crucial information to assist an investigation.

Earlier this year, the BBC dropped brand new episodes on a weekly basis, featuring haunting cases that left viewers horrified. Despite now broadcasting repeat episodes, viewers can still catch another instalment this week.

Tonight (Sunday, April 19), a further episode will air on BBC Two at 9pm, entitled Untraceable Guns. Viewers will be drawn into yet another gripping investigation as West Midlands Police make a stark discovery, shining a light on the chilling reality of undetectable weapons, reports the Mirror.

A BBC synopsis reads: "Firearms officers from West Midlands Police receive a tip-off about a local man with an unexpected arsenal of firearms. Inside a bedroom wardrobe are six guns, two of which they believe are 3D-printed assault weapons. Along with the guns, the police also find ammunition, a silencer and a 3D printer."

It continues: "The 30-year-old resident is arrested and taken into custody. He has no criminal record and no obvious links to organised crime, leaving police teams to ask whether he is an extremist, an arms dealer or simply a gun collector, as he claims to be. Is he creating these guns to use them, and could he have used them already?"

One IMDb reviewer had previously described the episode as an "unsettling watch", stating: "Wow, this was one totally uncomfortable and unsettling watch, in my absolute naivety, I honestly didn't think it was possible, there's always been that imagined security that The Police have a handle on weapons, who has what, how they got them etc, but when people can make their own, it's one chilling thought."

Since its initial broadcast in 2019, Forensics: The Real CSI has established itself as a firm favourite amongst true crime enthusiasts, with numerous viewers declaring it the "best" documentary series on television.

Discussing earlier episodes previously, one viewer posted on X: "I've watched hundreds of true crime documentaries and this is one of the most depraved."

Another commented: "#forensicstherealcsi that is one of the most disgusting cases I've seen." A third contributed: "This is compelling stuff #ForensicsTheRealCSI."

Over on Facebook, one viewer remarked: "I love this programme even better that 24hrs on police custody." Another stated: "This is the best TV programme." Writing on IMDb, one reviewer commented: "This is one of those rare series that completely changes how you look at crime investigation. Not because it dramatizes things, but because it does the exact opposite."

Another wrote: "I am so impressed at how this show has been formulated it keeps you captivated from beginning to end. It covers every aspect of the crime from 999 call to on scene investigation including how the for3nsic team cover every single conceivable piece of possible evidence and the ways in which they obtain information from these."

Forensics: The Real CSI returns tonight at 9pm on BBC Two. Episodes can also be streamed on BBC iPlayer.