delivered the opinion of the Court.
Petitioner pleaded guilty to an indictment charging him with robbery by means of a deadly weapon. The Circuit Court of Iron County, Missouri, found him guilty and sentenced him to the state penitentiary, where he is now confined, for a term of fifteen years on May 28, 1940. In April, 1944, he filed a petition for a writ of habeas corpus in the Supreme Court of Missouri. After reciting the foregoing facts concerning his conviction he further alleges in his petition:
“Prior to his conviction and sentence, as aforesaid, the petitioner requested the aid of counsel. At the time of his conviction and sentence, as aforesaid, the petitioner was without the aid of counsel, the Court did not make an appointment of counsel, nor did petitioner waive his constitutional right to the aid of counsel, and he was incapable adequately of making his own defense, in consequence of which he was compelled to plead guilty.”
And he contends that he was deprived of counsel contrary to the requirements of the due process clause of the Four*473teenth Amendment. The Supreme Court of Missouri allowed petitioner to proceed in forma pauperis but denied the petition for the reason that it “fails to state a cause of action.” The case is here on a petition for a writ of certiorari which we granted because of the substantial nature of the constitutional question which is raised.
Missouri has a statute which requires a court on request to assign counsel to a person unable to employ one and who is charged with a felony. Rev. Stat. 1939, § 4003. The Missouri Supreme Court did not indicate the reasons for its denial of the petition beyond the statement that the petition failed to state a cause of action. Whatever the grounds of that decision it is binding on us insofar as state law is concerned. Smith v. O’Grady, 312 U. S. 329. But the right to counsel in cases of this type is a right protected by the Fourteenth Amendment of the federal Constitution. The question whether that federal right has been infringed is not foreclosed here, even though the action of the state court was on the ground that its statute requiring the appointment of counsel was not violated. Powell v. Alabama, 287 U. S. 45, 59-60. And Missouri has not suggested in the argument before this Court that it provides a remedy other than habeas corpus for release from a confinement under a judgment of conviction obtained as a result of an unconstitutional procedure. Neither in the briefs nor in oral argument did Missouri suggest that its habeas corpus procedure (see Rev. Stat. 1939, §§ 1590, 1621, 1623) is not available in this situation.1
The petition for habeas corpus was denied without requiring the State to answer or without giving petitioner an opportunity to prove his allegations. And the allega*474tions contained in the petition are not inconsistent with the recitals of the certified copy of the sentence and judgment which accompanied the petition and under which petitioner is confined. Hence we must assume that the allegations of the petition are true. Smith v. O’Grady, supra. Read in that light we think the petition makes a prima jade showing of denial of the constitutional right. The Missouri Supreme Court has ruled that when a defendant requests counsel it will be “presumed,” in absence of evidence to the contrary (State v. Steelman, 318 Mo. 628, 631, 300 S. W. 743), that he was “without counsel and that he lacked funds to employ them.” State v. Williams, 320 Mo. 296, 306, 6 S. W. 2d 915. We indulge the same presumption. Certainly it may be reasonably inferred from that request and from the further allegation that as a result of the court’s failure to appoint counsel petitioner was “compelled to plead guilty,” that he was unable to employ counsel to present his defense because he was without funds. Like other judgments, a judgment based on a plea of guilty is not of course to be lightly impeached in collateral proceedings. See Johnson v. Zerbst, 304 U. S. 458, 468-469. But a plea of guilty to a capital offense made by one who asked for counsel but could not obtain one and who was “incapable adequately of making his own defense” stands on a different footing. Robbery in the first degree (Rev. Stat. 1939, § 4450) by means of a deadly weapon is a capital offense in Missouri. Rev. Stat. 1939, § 4453. The law of Missouri has important distinctions between robbery in the first degree, robbery in the second degree, grand larceny, and petit larceny.2 These involve technical requirements of the indictment or information, the kind of evidence required *475for conviction,3 the instructions necessary to define the several elements of the crime,4 and the various defenses which are available. These are a closed book to the average layman. These considerations underscore what was said in Powell v. Alabama, supra, p. 69: “Even the intelligent and educated layman has small and sometimes no skill in the science of law. If charged with crime, he is incapable, generally, of determining for himself whether the indictment is good or bad. He is unfamiliar with the rules of evidence. Left without the aid of counsel he may be put on trial without a proper charge, and convicted upon incompetent evidence, or evidence irrelevant to the issue or otherwise inadmissible. He lacks both the skill and knowledge adequately to- prepare his defense, even though he have a perfect one. He requires the guiding hand of counsel at every step in the proceedings against him. Without it, though he be not guilty, he faces the danger of conviction because he does not know how to establish his innocence. If that be true of men of intelligence, how much more true is it of the ignorant and illiterate, or those of feeble intellect.” Those observations are as pertinent in connection with the accused’s plea as they are in the conduct of a trial. The decision to plead guilty is a decision to allow a judgment of conviction to be entered without a hearing — a decision which is irrevocable and which forecloses any possibility of establishing innocence. If we assume that petitioner committed a crime, we cannot know the degree of prejudice which the denial of counsel caused. See Glasser v. United States, 315 U. S. 60, 75-76. Only counsel could discern from the facts whether a plea of not guilty to the offense charged or a *476plea of guilty to a lesser offense would be appropriate.5 A layman is usually no match for the skilled prosecutor whom he confronts in the court room. He needs the aid of counsel lest he be the victim of overzealous prosecutors, of the law’s complexity, or of his own ignorance or bewilderment.
These are reasons why the right to counsel is “fundamental.” Powell v. Alabama, supra,, p. 70; Grosjean v. American Press Co., 297 U. S. 233, 243-244; Avery v. Alabama, 308 U. S. 444, 447. They indicate the protection which the individual needs when charged with crime. Prompt and expeditious detection and punishment of crime are necessary for the protection of society. But that may not be done at the expense of the civil rights of the citizen. Law enforcement need not be inefficient when accommodated to the constitutional guarantees of the individual.
Powell v. Alabama, supra, p. 71, held that at least in capital offenses “where the defendant is unable to employ counsel, and is incapable adequately of making his own defense because of ignorance, feeble mindedness, illiteracy, or the like, it is the duty of the court, whether requested or not, to assign counsel for him as a necessary requisite of due process of law.” It follows from our construction of this petition that if the allegations are taken as true, petitioner was denied due process of law. It may well be that these allegations will turn out to be specious and unfounded. But they are sufficient under the rule *477of Powell v. Alabama to establish a deprivation of due process of law if their verity is determined. See Cochran v. Kansas, 316 U. S. 255. Cf. Walker v. Johnston, 312 U. S. 275.
As we have said, Missouri does not claim that habeas corpus is not available in this type of ease or that under Missouri law there is some procedure other than habeas corpus available to petitioner in which he may challenge the judgment of conviction on constitutional grounds. Missouri, however, does contend that the denial of counsel could have been challenged by petitioner by an appeal, that no appeal was taken, and that no extraordinary circumstances are shown which excuse that failure. Heretofore we have not considered a failure to appeal an adequate defense to habeas corpus in this type of case. Smith v. O’Grady, supra. Under these circumstances the failure to appeal only emphasizes the need of counsel. If an appeal were made such a requirement, the denial of counsel would in and of itself defeat the very right which the Constitution sought to protect.
It is suggested, moreover, that for all we know the denial of the petition by the Supreme Court of Missouri rested on adequate state grounds. It is a well established principle of this Court that before we will review a decision of a state court it must affirmatively appear from the record that the federal question was presented to the highest court of the State having jurisdiction and that its decision of the federal question was necessary to its determination of the cause. Honeyman v. Hanan, 300 U. S. 14, 18; Lynch v. New York, 293 U. S. 52. And where the decision of the state court might have been either on a state ground or on a federal ground and the state ground is sufficient to sustain the judgment, the Court will not undertake to review it. Klinger v. Missouri, 13 Wall. 257, 263; Wood Mowing & Reaping Machine Co. v. Skinner, 139 U. S. 293, 297; Allen v. Arguimbau, 198 U. S. 149, *478154-155; Lynch v. New York, supra. We adhere to those decisions. But it is likewise well settled that if the independent ground was not a substantial or sufficient one, “it will be presumed that the State court based its judgment on the law raising the Federal question, and this court will then take jurisdiction.” Klinger v. Missouri, supra, p. 263; Johnson v. Risk, 137 U. S. 300, 307; Lawrence v. State Tax Commission, 286 U. S. 276, 282-283. Thus in Maguire v. Tyler, 8 Wall. 650, and in Neilson v. Lagow, 12 How. 98, 110, it was contended that the judgments rested on adequate state grounds. In neither was there an opinion of the state court. The Court examined the record, found the state grounds not substantial or sufficient, and reversed the judgments on the federal question.6 We think the principle of those cases is applicable here. The petition establishes on its face the deprivation of a federal right. The denial of the petition on the grounds that it fails to state a cause of action strongly suggests that it was denied because there was no cause of action based on the federal right. And when we search for an independent state ground to support the denial, we find none. The Attorney General of Missouri only goes so far as to say that the petition did not state facts sufficient to< justify the appointment of counsel under the Missouri statute. But as we have seen, the allegations in the petition seem sufficient under the rule laid down by the Supreme Court of Missouri in State v. Williams, supra. And Missouri suggests no other state ground which *479might be the basis of the decision.7 That is to say, the only state grounds which have been advanced in support of the decision below appear to be insubstantial. We can only assume therefore that the denial by the Supreme Court of Missouri was for the reason that the petition stated no cause of action based on the federal right. That seems to us to be the fair intendment of the language which it used if we put to one side, as we must, the insubstantial state grounds which have been advanced in explanation of the denial. If perchance the Supreme Court of Missouri meant that some reason of state law precludes a decision of the federal question, that question is not foreclosed by this decision. Cf. State Tax Commission v. Van Cott, 306 U. S. 511; Minnesota v. National Tea Co., 309 U. S. 551. But on the present state of the record before us, we do not see what more petitioner need do to establish the federal right on which his petition is based.
Reversed.
It is available to challenge tbe constitutionality of the statute on which the judgment of conviction rests. Ex parte Smith, 135 Mo. 223, 36 S. W. 628; Ex parte Taft v. Shaw, 284 Mo. 531, 538-539, 225 S. W. 457; Ex parte McKean, 338 Mo. 597, 600, 92 S. W. 2d 141.
Thus one indicted for robbery in the first degree cannot be convicted of robbery in the second degree but may be convicted of larceny. State v. Jenkins, 36 Mo. 372; State v. Davidson, 38 Mo. 374; State v. Brannon, 55 Mo. 63.
See State v. White, 326 Mo. 1000, 34 S. W. 2d 79.
See State v. Brown, 104 Mo. 365, 16 S. W. 406; State v. Woodward, 131 Mo. 369, 33 S. W. 14; State v. McLain, 159 Mo. 340, 60 S. W. 736.
“Robbery in the first degree without the use of a dangerous and deadly weapon is included in the charge of robbery by means of such weapon. Larceny is also so included, and where the charge is robbery and there is evidence of a larcenous taking of property but the element of force such as to constitute the offense of robbery is wanting there should be an instruction submitting larceny.” State v. Craft, 338 Mo. 831, 843, 92 S. W. 2d 626. And see State v. Weinhardt, 253 Mo. 629, 161 S. W. 1151.
In the following eases the Court without benefit of an opinion of the state court examined the pleadings, found substantial state grounds on which the judgment might have rested, and dismissed the writ. Johnson v. Risk, supra; Allen v. Arguimbau, supra; Bachtel v. Wilson, 204 U. S. 36; Adams v. Russell, 229 U. S. 353; Cuyahoga River Power Co. v. Northern Realty Co., 244 U. S. 300, 303; Lynch v. New York, supra; Woolsey v. Best, 299 U. S. 1; McGoldrick v. Gulf Oil Corp., 309 U. S. 2.
It is stated that the petition does not allege facts which show that petitioner was denied a fair trial, that he was ignorant, that he was innocent, or that the court was prejudiced. But it is not apparent how the addition of any such allegations to the petition would be relevant to petitioner’s cause of action based on the constitutional right to counsel. We are not referred to any Missouri law which would make them relevant.