IANAL, but I’ve got access to Lexis and was bored…
Allow me to dispel a common preconception. At common law (think England, 1700s), the Seinfeld crew absolutely, positively were guilty of a crime – called misprision of a felony. Essentially, it means “failure to report a felony.” Felonies are serious crimes, such as murder, kidnapping, rape, robbery, and the like. A forcible carjacking – the crime committed in the final episode of Seinfeld – would therefore qualify, and the Seinfeld crew could be in deep do-do with the local sheriff.
“If A and B be fighting and C, a man of full age, comes by chance, and is a looker on only, and assists neither, he is not guilty of murder or homicide, as principal in the second degree, but is a misprision, for which he shall be fined, unless he use means to apprehend the felon.” 1 Hale, Pleas of the Crown, 439, as quoted in Clark & Marshall, A Treatise on the Law of Crimes § 8.02 (7th ed. 1967). Clark & Marshall § 8.02, p. 511, n. 15, also quotes 2 Hawkins, Pleas of the Crown, c. 29, § 10 on the matter: “‘Those who, by accident, are barely present when a felony is committed, and are merely passive, and neither in any way encourage it, nor endeavor to hinder it, nor to apprehend the offenders, shall neither be adjudged principles [sic] nor accessories; yet, if they be of full age, they are highly punishable by fine and imprisonment for their negligence, both in not endeavoring to prevent the felony, and in not endeavoring to apprehend the offender.’”
According to Blackstone, the crime at common law consisted merely in the “concealment of a felony which a man knows, but never assented to; for if he assented this makes him either principal or accessory.” 4 W. Blackstone, Commentaries *121. See Clark & Marshall, A Treatise on the Law of Crimes § 8.14 (7th ed. 1967); R. Perkins, Criminal Law 512 (2d ed. 1969); L. Hochheimer, Crimes and Criminal Procedure § 39 (1st ed. 1897).
“[T]here is reason to believe that misprision of felony as defined by Blackstone is merely one phase of the system of communal responsibility for the apprehension of criminals which received its original impetus from William I, under pressure of the need to protect the invading Normans in hostile country, and which endured up to the Seventeenth Century in England. In order to secure vigilant prosecution of criminal conduct, the vill or hundred in which such conduct occurred was subject to fine, as was the tithing to which the criminal belonged, and every person who knew of the felony and failed to make report thereof was subject to punishment for misprision of felony. Compulsory membership in the tithing group, the obligation to pursue criminals when the hue and cry was raised, broad powers of private arrest, and the periodic visitations of the General Eyre for the purpose of penalizing laxity in regard to crime, are all suggestive of the administrative background against which misprision of felony developed. With the appearance of specialized and paid law enforcement officers, such as constables and justices of the peace in the Seventeenth Century, there was a movement away from strict communal responsibility, and a growing tendency to rely on professional police.” 8 U. Chi. L. Rev. 338, 340-341 (1941) (footnotes omitted).
Glazebrook, Misprision of Felony – Shadow or Phantom?, 8 Am. J. of Legal History 189 and 283 (1964) cites eminent authority that in England the offense fell “into desuetude.” Id. at 300. According to Glazebrook, there was no “reported decision during the four hundred years since the offence first crept into a book,” and no book before J. Chitty, A Practical Treatise on the Criminal Law (2d ed., London 1826) contained “a precedent of an indictment for misprision of felony.” Id. In any event, if the crime had died, it was resurrected by the House of Lords in H. L. Sykes v. Director of Public Prosecution, [1961] 3 All E. R. 33. Lord Denning stated that “it is plain that there is and always has been an offence of misprision of felony and that it is not obsolete.” Id. at 40. Sykes acknowledged only two necessary elements, knowledge and concealment. “[M]isprision requires nothing active. The failure or refusal to disclose the felony is enough.” Id. at 41. This followed the Blackstone definition.
Note that no American jurisdiction currently allows for prosecutions for the common law offense of misprision of a felony. See, e.g., Pope v. State, 396 A.2d 1054 (Md. 1978). However, a number have statutes on the books that make failure to report a crime a misdemeanor.
BUT – let us now distinguish between the failure to report a crime and the failure to rescue, which is about what the OP asks.
There are seven major avenues the courts have utilized to impose a criminal duty to act. These methods of ascribing criminal culpability for failure to aid have been cataloged by several commentators. See, e.g., Wayne R. LaFave & Austin W. Scott, Jr., Criminal Law 203-07 (2d ed. 1986) (from which I am shamelessly paraphrasing).
A duty to act based upon the relationship of the parties: This is the most common area of criminal imposition of a duty to aid another. This obligation arises from what society sees as a special and more complex relationship between the parties. This special relationship of the parties justifies the added burden of forcing action or penalizing inaction. Examples involve parents who have a legal duty to aid their children, see, e.g., Cal. Penal Code 270, 273(a) (West 1988 & Supp. 1997), adult children who have a duty to aid their aging parents, see, e.g., Cal. Penal Code 270c (West 1988 & Supp. 1997), spouses who have a duty to care for each other, see, e.g., Commonwealth v. Konz, 450 A.2d 638, 641-42 (Pa. 1982), and a ship’s captain who has a duty to assist those under his care, see, e.g., United States v. Knowles, 26 F. Cas. 800, 802 (N.D. Cal. 1864).
A duty to act based upon contract: Sometimes the duty to act and the criminal responsibility imposed for failure to act are based upon contract. A security person hired to protect another cannot fail to perform the duties he contracted to complete. If his failure to act causes physical harm to another, the individual with the duty will be held criminally liable. See, e.g., People v. Montecino, 152 P.2d 5, 13 (Cal. App. 1944).
A duty based upon a voluntary assumption of care: Sometimes, one comes to the aid of another in a “half-hearted” or ineffective way. In such situations, even if the helper initially had no duty to come to the aid of the victim, her act of voluntarily undertaking assistance may create a duty to continue to aid the victim until the victim is safe. For example, a person sees an accident on the roadway and stops to render aid. While this initial volunteer is attempting to help the victim, several other motorists stop to see if “there is anything they can do.” The initial volunteer tells the other would-be assistants that they can leave because the situation is under control. The other potential helpers leave. The initial volunteer then realizes she is late for an appointment and simply leaves. Criminal liability has been imposed on persons who, like the initial volunteer in the example, take on the responsibility to assist another but fail to do everything necessary to assist the victim. See, e.g., Jones v. United States, 308 F.2d 307 (D.C. Cir. 1962).
A duty may arise from the fact that the person created the risk from which the need for protection arose: The most obvious example of this type of legal responsibility is when the person engages in a physical altercation with another, rendering that person incapable of taking care of himself. When the person still standing simply leaves the scene without rendering assistance, criminal liability for the outcome may result. In these circumstances, one can be held criminally liable for the consequence of not assisting the victim. See, e.g., People v. Fowler, 174 P. 892 (Cal. 1918).
A duty can arise from a special relationship that makes the non-acting partner criminally responsible for the actor’s criminal action: The most often used example of this legal duty is where a parent is held criminally liable for the criminal conduct of a child when the parent fails to “control” the minor child. See, e.g., Cal. Penal Code 490.5 (West Supp. 1997).
A duty can arise from the fact that one owns the real property upon which the victim is injured: A bar owner, for example, may be held criminally liable when his patrons die or suffer injury. See Commonwealth v. Welansky, 55 N.E.2d 902 (Mass. 1944).
The duty to act and the resulting criminal liability for failing to act, based upon statute: This duty to act is based upon a statute requiring such action rather than any special relationship between the victim and the assisting party. The legislature may, with some constitutional limitations, impose the legal duty to come to the aid of others to whom the assisting party has no obvious connection or obligation. See, e.g., Vt. Stat. Ann. tit. 12, 519 (1973). The Vermont statute provides the following: (a) A person who knows that another is exposed to grave physical harm shall, to the extent that the same can be rendered without danger or peril to himself or without interference with important duties owed to others, give reasonable assistance to the exposed person unless that assistance or care is being provided by others. (b) A person who provides reasonable assistance in compliance with subsection (a) of this section shall not be liable in civil damages unless his acts constitute gross negligence or unless he will receive or expects to receive remuneration. Nothing contained in this subsection shall alter existing law with respect to tort liability of a practitioner of the healing arts for acts committed in the ordinary course of his practice. © A person who willfully violates subsection (a) of this section shall be fined not more than $ 100.00. Id.