delivered the Opinion of the Court.
We granted certiorari to review the court of appeals’ ruling that a defendant on trial for homicide should have been allowed to present evidence of inadequate medical treatment as the intervening cause of the victim’s death.
See People v. Saavedra-Rodriguez,
I.
On September 9, 1994 the defendant, Pa-tricio Saavedra-Rodriguez, stabbed Pedro Avila in the chest. The victim was found by his roommates and brought to the hospital by ambulance. Upon arrival at North Colorado Medical Center, the victim was treated by an emergency room doctor, Dr. Claman; a surgeon, Dr. Wikholm; and several nurses. Despite treatment, the victim’s condition deteriorated and he did not survive. According to the autopsy, the victim died of a stab wound that penetrated approximately four and one-half inches into the victim’s chest cavity, punctured his lung, and cut a one-inch hole in his heart.
During treatment of the victim, Drs. Cla-man and Wikholm disagreed about the severity of the wound, the appropriate course of treatment, and whether to continue resusci-tative measures. Dr. Claman subsequently filed an “incident report” with the hospital criticizing Dr. Wikholm’s treatment. The hospital’s internal peer review concluded that Dr. Wikholm failed to provide “aggressive trauma management.”
The defendant was charged with second-degree murder. Based upon the victim’s medical records and interviews with hospital personnel, who were involved in the victim’s care, the defendant sought to raise an intervening cause defense. The prosecution moved to prevent the defense based on its argument that, although Dr. Wikholm’s care-may have been substandard, it did not rise to the level of an intervening cause.
At the pretrial hearing on the prosecution’s motion to prevent the defendant from presenting an intervening cause defense, the parties disputed the standard of proof required for an intervening cause defense. The prosecution argued that the defendant had the burden of proving within a reason *225 able degree of medical certainty that Dr. Wikholm’s gross negligence caused the death. The defense argued that, in order to raise the defense, there need be only a scintilla of evidence to support an intervening cause theory.
The defense made an offer of proof as to the testimony of a number of medical practitioners. This testimony would have been that Dr. Wikholm made several errors in his diagnosis and treatment of the victim. Additional testimony would have been that Dr. Wikholm unnecessarily delayed treatment and that given proper timely treatment the patient may have had a better chance of survival. Finally, the defense would have offered testimony that the patient survivability rate after a heart wound is higher than 50% and in certain circumstances increases to 80% if afforded proper treatment.
Although the defendant offered to present testimony of doctors and nurses who were critical of Dr. Wikholm’s care, he did not offer testimony that Dr. Wikholm’s allegedly substandard care was the cause of the victim’s death. In fact, all of the doctors would have testified that the cause of the victim’s death was the stab wound inflicted by the defendant.
In a written order issued on October 19, 1995, the trial court disallowed the defendant’s intervening cause defense. The court found that, according to
People v. Calvaresi,
The defendant was found guilty of manslaughter as a lesser-included offense of second-degree murder, and the trial court entered a judgment of conviction. The court of appeals reversed the conviction and ordered a new trial.
See Saavedra-Rodriguez,
We agree with the trial court. We hold that improper medical treatment does not relieve the defendant of liability for the death of the victim unless the treatment is grossly negligent and death probably would not have otherwise occurred. Therefore, we reverse the judgment of the court of appeals.
II.
In order to resolve the issue before us, we must first set forth the essential components of an intervening cause defense in criminal law. We then define the quantum of evidence necessary to raise this issue before a jury and determine whether the defendant’s offer of proof met this standard.
A
A conviction for criminal homicide requires proof beyond a reasonable doubt that death was a natural and probable consequence of the defendant’s unlawful act.
See Hamrick v. People,
In Calvaresi, we adopted Wharton’s rule on intervening cause:
To warrant a conviction for homicide, the death must be the natural and probable consequence of the unlawful act, and not the result of an independent intervening cause in which the accused does not participate, and which he could not foresee. If it appears that the act of the accused was not the proximate cause of the death for which he is being prosecuted, but that another cause intervened, with which he was in no way connected, and but for which death would not have occurred, such supervening cause is a defense to the charge of homicide.
1 Ronald A. Anderson,
Wharton’s Criminal Law and Procedure
§ 200, at 448 (12th ed.1957);
see Calvaresi,
For an independent intervening cause to relieve a defendant of liability it must not be reasonably foreseeable. Simple negligent medical treatment, although hopefully unusual, is sufficiently ordinary that we consider it foreseeable. “[Njegligence, unfortunately, is entirely too frequent a human conduct to be considered ‘abnormal’ ”.
Calvaresi,
In
Calvaresi,
we recognized that unlike simple negligence, gross negligence is sufficiently extraordinary to be classified as unforeseeable.
See
We have established that gross negligence is unforeseeable. However, in order for the gross negligence to discharge the defendant of liability for homicide, the maltreatment must also be the cause but for which death would not have occurred.
See People v. Fite,
We are concerned that this component, the cause but for which death would not have occurred, could be misunderstood as merely requiring an event in a sequence of events which produced death. Indeed, this appears to be the misunderstanding of the court of appeals, which stated that grossly negligent delay in diagnosing and treating could amount to an intervening cause if proper treatment would have saved the victim’s life. Rather, in order for grossly negligent medical treatment to relieve the defendant of liability, it must interrupt the natural and probable sequence of events to cause death. This interruption only occurs when death would not have been the probable and natural result without the grossly negligent medical treatment.
To determine whether grossly negligent medical treatment was the cause of death, we look to the initial trauma to the victim as well as to the nature of the improper treatment. We consider the defendant’s act, the nature of the wound inflicted by the defendant, the location of the wound on the victim, the natural and probable result of the
*227
injury, and the actual result of the medical treatment. The inquiry should focus on whether the wound inflicted by the defendant is the type of wound that would generally endanger or destroy life and from which the victim would likely die if little or no treats ment is provided. Accordingly, a defendant is not relieved of liability, even in the face of grossly negligent medical treatment, if the original wound would likely have been fatal without the treatment.
See
Arthur Leavens,
A Causation Approach to Criminal Omissions,
76 Cal. L.Rev. 547, 597 (1988). Conversely, if the wound inflicted upon the victim would probably not have been fatal, but the victim dies as a result of the physician’s grossly negligent treatment, the physician’s gross negligence is an intervening act that relieves the defendant of criminal liability for the death.
See Noble v. State,
We find it persuasive that other courts have also drawn distinctions based upon the seriousness of the original wound.
See Tibbs v. Commonwealth,
Our holding, that grossly negligent medical treatment is not an intervening cause of death unless the initial wound would not have been fatal without treatment, is consistent with our analysis in
Calvaresi.
1
See
Although the sole cause testimony offered in Calvaresi was more than adequate evidence that death may not have resulted absent the grossly negligent medical treatment, we made it clear that the defendant need not provide evidence that the intervening act rise to the level of the sole cause of death.
We specifically directed that the jury be informed of Wharton’s rule.
See id.
at 283,
In sum, in order to discharge a defendant of liability for homicide, an intervening act must be an unforeseeable act but for which the victim would not have died. Grossly negligent medical treatment is not foreseeable. Thus, if the treatment is grossly negligent and the wound inflicted by the defendant would not have been likely to cause death absent the medical treatment, the medical treatment constitutes an independent intervening act relieving the defendant of liability for the victim’s death.
B.
Having explained the essential components of the intervening cause defense, we now consider the quantum of evidence necessary to raise this defense and determine that the defendant’s offer of proof did not meet this standard. The defendant contends that, even if the trial court was convinced that the doctor’s care did not constitute gross negligence such that it would be an intervening cause, he should not have been precluded
*228
from presenting the defense to the jury. Although the causation element must be submitted to the jury, all potential defenses to the element are not jury issues.
See Lybarger v. People,
The quantum of evidence that must be offered by the defendant in order to be entitled to an instruction on a theory of defense is “a scintilla of evidence”.
See People v. Lundy,
The remaining issue is whether the defendant presented sufficient evidence to allow the defense to be considered by the trier of fact. The defendant contends that his offer of proof evinces that had adequate medical treatment been provided, the victim would have had a greater chance of survival. The court must view the defendant’s offer of proof in the light most favorable to the defendant and draw all reasonable inferences therefrom. However, assuming the truth of the defendant’s offer of proof, evidence that adequate medical care might have prevented death does not show that the medical care that was provided actually caused death. Whether the victim would have had a better chance of survival with proper medical care is a different inquiry from whether he would have been likely to survive absent the medical care he received. Because the defendant’s criminal liability is premised, in part, on the nature of the wound inflicted by the defendant, the victim’s chance of survival, given proper care, is only relevant to consider whether the wound was of the type likely to result in death had little or no treatment been provided. We must also consider the defendant’s act, the nature of the wound inflicted by the defendant, the location of the wound on the victim, the natural and probable result of the injury, and the impact of the treatment on the victim. A failure to provide or select the best treatment, and therefore save the victim, should not relieve the original assailant of liability if the wound was of the type likely to result in death if little or no treatment had been provided. See Lawrence Crocker, A Retributive Theory of Criminal Causation, 1994 J. Contemp. Legal Issues 65, 95.
Here the defendant did not meet the foundational requirements necessary to present an affirmative defense. The defendant offered proof of improper medical care. He failed to offer any evidence that would show that the victim’s wound was unlikely to result in death had little or no treatment been provided. Therefore, he has not offered evidence that Dr. Wikholm’s medical care may have caused the victim’s death. Thus, the defendant has not offered a scintilla of evidence that the medical care constituted gross negligence absent which death would not have occurred. In order to present an intervening cause defense to the jury, the defendant must present evidence that the natural chain of causation flowing from the defendant’s act was broken, as where, “the defendant did not inflict a fatal wound and the victim died only from the effects of the subsequent act.” See Wayne R. Lafave et al., Substantive Criminal Law, Basic Premises of the Criminal Law § 3.12, at 406 (1986).
We agree with the trial court that the treatment provided did not change the course of natural effects that flowed from the stab wound to the victim’s heart. Considering the defendant’s act, the nature of the wound inflicted by the defendant, the location *229 of the wound on the victim, the natural and probable result of the injury, and the impact of the treatment on the victim, we conclude that such a wound is the type of wound likely to result in death. Since the defendant did not lay a proper foundation as to the existence of an intervening cause defense, the trial court was correct to withhold the evidence from the jury.
The trial court’s ruling is consistent with our holding in
Fite.
In Fite, the defendant shot her husband.
See Fite,
The trial court’s ruling is also consistent with our holding in
Calvaresi
where the defense offered the testimony of two doctors who claimed that the treating doctor’s negligence was the
sole
cause of the victim’s death.
See
Here, the defendant offered testimony that the victim might have survived the injury had he been given immediate and proper treatment. However, he did not offer any evidence to show that the physician’s treatment was the sole cause of death. Nor did he meet the lesser standard that the victim would have been likely to survive absent the medical care that was provided. Accordingly, the trial court correctly excluded evidence of deficient medical care because there was no evidence that the medical care was the cause of death.
III.
In sum, improper medical treatment is an intervening cause of death only if it is grossly negligent and the initial wound would not likely have been fatal without the treatment. A defendant need only offer some evidence that the medical treatment was the intervening cause of death to be entitled to submit the defense to a jury. Accordingly, we reverse the court of appeals and remand with directions to consider any unresolved issues.
Notes
. In Calvaresi it was not necessary for us to discuss whether the victim’s shoulder wound was of the type generally likely to cause death because the issue before us concerned the jury instruction, not whether the evidence should be submitted to the jury.
. The only medical testimony came from the general surgeon, who was the attending physician.
See Fite,
