IANAL but based on my understanding, manslaughter generally includes some form of negligence (instead of premeditation like homicide) so until our laws and culture catch up to the power these developers/decision makers actually hold, it's unlikely that a jury would blame the developers (or that a judge would even be sympathetic to the argument). Our society has agreed long ago that drinking and driving is irresponsible so thats why drunk driving fatalities are often prosecuted as manslaughter but the same is not true of software engineers and their creations. We need a sweeping cultural change outside of software engineering just like we had with civil engineers in the 20th century.

Nowadays, a professional engineer (a phrase with a precise legal meaning) can be held criminally and civilly liable for negligence even when they are "just following irders." Unfortunately, we're at the very early wild wild west stages of the industry, before some big exposé or calamity completely shakes up the industry (i.e. Sinclair's The Jungle did for food, Carson's Silent Spring for pesticide use, or the 1906 SF earthquake for building codes).