[4] Relentless Software CEO Andrew Eades explained that while Blue Toad Murder Files was originally conceived as a PlayStation 3 DualShock game, it translated well to a touch pad interface.

[5] The developers wanted to swap that game's cartoony family-targeted style for something more gritty, dramatic, and adult; therefore the franchise was split in two, becoming Murder Files: The Enigma Express and The Trace.

"[8] Many conversations were had between Varela and the game's producers regarding "just how dark we could go"; in particular two areas of contention were the state of Warren Oakley when the player finds him, and the injuries sustained by the dog Floyd.

The aim was to make the player "feel like they were connecting clues and solving the case", so considerable effort was done to decide how to realise this without creating something too complex.

[6] The player assumes the role of Baltimore police detective Sam Pearce, who begins the game investigating a suicide which is later revealed to be a murder which leads to a series of chain events.

Throughout the game, Pearce calls his lab partner Alex to discuss what is known so far, to follow up of potential leads, and to receive the results of tested DNA.

[2] The game "combines The Room-style screen poking, point and click puzzle solving, and hidden object hunting – and gives it a crime-solving twist.

[3] The game lacks a hint system but allows player to tweet for help via the #SolveTheTrace hashtag if they get stuck,[15] or post to social media like Facebook where they will likely receive a reply from Relentless.

Many liked the well-written logical murder-mystery plot, and have deemed it one of the few satisfying iOS games of the genre along with Detective Grimoire and the Sherlock Holmes PC series.

Similarly, the engrossing and immersive nature of the game, which is played in a first-person perspective (by a character who realistically comments on clicked objects) was highly praised.

However, the game was criticised for not being long enough and being too expensive, for lacking in difficulty and re-playability, for having slightly imprecise/finicky/clunky controls, for not having Pierce and Alex voiced, and for being linear or streamlined.

[14] A different Pocket Gamer article praised its ability to unpatronisingly "allow the player to untangl[e] the leads and establish...the connections" all on their own, rather than making them "the Watson to the protagonist's Sherlock", deeming the game "pleasant if not pulse-pounding".

[21] The Daily Herald said the "well-constructed, compelling app" required "a sharp eye" and "a willingness to think outside the box", adding that while "not violent or particularly realistic", the game may upset younger or sensitive players.

The site described the branching diagram players use to test hypotheses and make deductions as "a very nice device that forwards the game's narrative without breaking the immersion.

[29] The Arts Desk described the game as a "one-man mashup of CSI and Columbo" with "simple, slightly silly" cases when compared to the "emotionally wrung-through gut punches" of True Detective and Heavy Rain, concluding "this is the emotionally light and intellectually undemanding videogame equivalent of a Murder She Wrote or Quincy case – and has a similarly clichéd and homely charm".

[30] Gamezebo described the serious, thoughtful atmosphere, and the detective's "sardonic sense of humor"; the site praised the game's "minimalist, mostly menu-less style", which turned everyday actions into immersive "fun gameplay mechanics".