When did the discovery/disclosure rules as we know them today
In the United States, the constitutional right to criminal discovery was established in Brady v. Maryland, 373 U.S. 83 (1963).
A law review article written in 1961, meanwhile, bemoaned how inferior discovery for defendants in criminal cases was relative to discovery in civil litigation, analyzing the state of affairs in U.S. criminal discovery law two years earlier.
Notably, two pre-Brady cases decided by the U.S. Supreme Court had held that providing discovery to criminal defendants was not constitutionally required. Leland v. Oregon, 343 U.S. 790 (1952); Cicenia v. LaGay, 357 U.S. 504 (1958). Many state criminal justice systems took the same position.
Anatomy of a murder (1959) accurately reflected that aspect of U.S. criminal procedure at the time it was set in.
were criminal discovery rules in the US indeed virtually non-existent
back in the 1950s? Did defense attorneys have to basically fly by the
seat of their pants?
The modern U.S. criminal justice system's protections of the constitutional rights of criminal defendants were mostly absent in the 1950s.
But, primarily in the decade from 1961-1970, the U.S. Supreme Court held that the criminal procedure protections of the U.S. Bill of Rights applied to state courts and interpreted those protections in a way that made those constitutional protections for criminal defendants meaningful.
Prior to this constitutional criminal justice revolution, most states were far less solicitous of criminal defendants' rights, although some states provided more than the bare minimum of protections to criminal defendants, either due to state statutes and court rules, or due to state constitutional protections that were interpreted in a manner that gave them real meaning.
Prior to Miranda v. Arizona, 384 U.S. 436 (1966), confessions obtained with pretty much anything short of several days of torture in police custody were admissible in evidence. A year earlier, in Griffin v. California, 380 U.S. 609 (1965), the United States Supreme Court held that it is a violation of a defendant's Fifth Amendment rights for the prosecutor to comment to the jury on the defendant's declining to testify, or for the judge to instruct the jury that such silence is evidence of guilt, something that also greatly limited the U.S. Constitutional right not to self-incriminate oneself. Confessions obtained under what would now clearly be considered to be duress and unlawful were routinely used to obtain confessions prior to these rulings.
Prior to Mapp v. Ohio, 367 U.S. 643 (1961), criminal defendants did not have a constitutional right to have illegally obtained evidence excluded from their trials in state courts. The exclusionary rule was a major change from pre-Mapp criminal procedure in most states.
Prior to Gideon v. Wainwright, 372 U.S. 335 (1963), indigent criminal defendants did not have the right to have a lawyer appointed for them as state expense. A lack of access to a lawyer for indigent defendants was the norm, prior to this ruling.
Prior to Duncan v. Louisiana, 391 U.S. 145 (1968), there was not a U.S. constitutional right to a jury trial in criminal cases in state court. In practice, however, essentially every U.S. state with a common law legal system (i.e. every state except Louisiana) provided criminal defendants in serious criminal case with a right to a jury trial anyway.
Prior to Pointer v. Texas, 380 U.S. 400 (1965), there was not a U.S. constitutional right to cross-examine witnesses against a criminal defendant in state court. Most U.S. states did have the hearsay rule in criminal cases, but the requirements of the confrontation clause protections of the Bill of Rights in criminal cases are more rigorous.
Prior to Washington v. Texas, 388 U.S. 14 (1967), criminal defendants did not have a U.S. constitutional right to force the attendance of witnesses for their side in state courts. Most U.S. states allowed criminal defendants to subpoena witness by the 1950s, but there were laggard states that did not, like Texas.
Prior to In re Winship, 397 U.S. 358 (1970), criminal defendants did not have a U.S. constitutional right to have all facts necessary to established their guilt of the crime they are charged with proven beyond a reasonable doubt in state court. Most states followed this rule most of the time, prior to 1970, but it was not a uniform or absolute rule in state courts, at least on some issues presented in criminal cases.
The U.S. Constitution still does not give criminal defendants a constitutional right to a direct appeal of their conviction, although it does create a right to a petition for habeas corpus (which is narrower in the grounds for which relief can be granted than a direct appeal), and the U.S. Constitution does protect the rights of criminal defendants in connection with a direct appeal of a conviction if a state makes it available. In practice, every U.S. jurisdiction affords criminal defendants this procedural protection anyway, however.
There were no direct appeals of right in federal court criminal cases until the 1890s when the U.S. Courts of Appeal were created, and the scope of habeas corpus petition protections prior to that point in time were very narrow. Habeas corpus petitions were routinely dismissed if a court with jurisdiction over the case had convicted a defendant of a crime and that defendant had not yet completed the sentence imposed.