728 PHIL. 578
BERSAMIN, J.:
That on or about May 17, 1995, in the City of Manila, Philippines, the said accused, being then an anesthesiologist at the Ospital ng Maynila, Malate, this City, and as such was tasked to administer the anesthesia on three-year old baby boy GERALD ALBERT GERCAYO, represented by his mother, MA. LUZ GERCAYO, the former having been born with an imperforate anus [no anal opening] and was to undergo an operation for anal opening [pull through operation], did then and there willfully, unlawfully and feloniously fail and neglect to use the care and diligence as the best of his judgment would dictate under said circumstance, by failing to monitor and regulate properly the levels of anesthesia administered to said GERALD ALBERT GERCAYO and using 100% halothane and other anesthetic medications, causing as a consequence of his said carelessness and negligence, said GERALD ALBERT GERCAYO suffered a cardiac arrest and consequently a defect called hypoxic encephalopathy meaning insufficient oxygen supply in the brain, thereby rendering said GERALD ALBERT GERCAYO incapable of moving his body, seeing, speaking or hearing, to his damage and prejudice.
Contrary to law.[14]
WHEREFORE, premises considered, the Court finds accused DR. FERNANDO P. SOLIDUM GUILTY beyond reasonable doubt as principal of the crime charged and is hereby sentenced to suffer the indeterminate penalty of TWO (2) MONTHS and ONE (1) DAY of arresto mayor as minimum to ONE (1) YEAR, ONE (1) MONTH and TEN (10) DAYS of prision correccional as maximum and to indemnify, jointly and severally with the Ospital ng Maynila, Dr. Anita So and Dr. Marichu Abella, private complainant Luz Gercayo, the amount of P500,000.00 as moral damages and P100,000.00 as exemplary damages and to pay the costs.
Accordingly, the bond posted by the accused for his provisional liberty is hereby CANCELLED.
SO ORDERED.[17]
WHEREFORE, premises considered, the Court finds accused Dr. Fernando Solidum, guilty beyond reasonable doubt as principal of the crime charged and is hereby sentenced to suffer the indeterminate penalty of two (2) months and one (1) day of arresto mayor as minimum to one (1) year, one (1) month and ten (10) days of prision correccional as maximum and to indemnify jointly and severally with Ospital ng Maynila, private complainant Luz Gercayo the amount of P500,000.00 as moral damages and P100,000 as exemplary damages and to pay the costs.
Accordingly, the bond posted by the accused for his provisional liberty is hereby cancelled.[19]
The case appears to be a textbook example of res ipsa loquitur.
x x x x
x x x [P]rior to the operation, the child was evaluated and found fit to undergo a major operation. As noted by the OSG, the accused himself testified that pre-operation tests were conducted to ensure that the child could withstand the surgery. Except for his imperforate anus, the child was healthy. The tests and other procedures failed to reveal that he was suffering from any known ailment or disability that could turn into a significant risk. There was not a hint that the nature of the operation itself was a causative factor in the events that finally led to hypoxia.
In short, the lower court has been left with no reasonable hypothesis except to attribute the accident to a failure in the proper administration of anesthesia, the gravamen of the charge in this case. The High Court elucidates in Ramos vs. Court of Appeals 321 SCRA 584 –In cases where the res ipsa loquitur is applicable, the court is permitted to find a physician negligent upon proper proof of injury to the patient, without the aid of expert testimony, where the court from its fund of common knowledge can determine the proper standard of care. Where common knowledge and experience teach that a resulting injury would not have occurred to the patient if due care had been exercised, an inference of negligence may be drawn giving rise to an application of the doctrine of res ipsa loquitur without medical evidence, which is ordinarily required to show not only what occurred but how and why it occurred. When the doctrine is appropriate, all that the patient must do is prove a nexus between the particular act or omission complained of and the injury sustained while under the custody and management of the defendant without need to produce expert medical testimony to establish the standard of care. Resort to res ipsa loquitur is allowed because there is no other way, under usual and ordinary conditions, by which the patient can obtain redress for injury suffered by him.
The lower court has found that such a nexus exists between the act complained of and the injury sustained, and in line with the hornbook rules on evidence, we will afford the factual findings of a trial court the respect they deserve in the absence of a showing of arbitrariness or disregard of material facts that might affect the disposition of the case. People v. Paraiso 349 SCRA 335.
The res ipsa loquitur test has been known to be applied in criminal cases. Although it creates a presumption of negligence, it need not offend due process, as long as the accused is afforded the opportunity to go forward with his own evidence and prove that he has no criminal intent. It is in this light not inconsistent with the constitutional presumption of innocence of an accused.
IN VIEW OF THE FOREGOING, the modified decision of the lower court is affirmed.
SO ORDERED.[21]
I.
THE HONORABLE COURT OF APPEALS ERRED IN AFFIRMING THE DECISION OF THE LOWER COURT IN UPHOLDING THE PETITIONER’S CONVICTION FOR THE CRIME CHARGED BASED ON THE TRIAL COURT’S OPINION, AND NOT ON THE BASIS OF THE FACTS ESTABLISHED DURING THE TRIAL. ALSO, THERE IS A CLEAR MISAPPREHENSION OF FACTS WHICH IF CORRECTED, WILL RESULT TO THE ACQUITTAL OF THE PETITIONER. FURTHER, THE HONORABLE COURT ERRED IN AFFIRMING THE SAID DECISION OF THE LOWER COURT, AS THIS BREACHES THE CRIMINAL LAW PRINCIPLE THAT THE PROSECUTION MUST PROVE THE ALLEGATIONS OF THE INFORMATION BEYOND REASONABLE DOUBT, AND NOT ON THE BASIS OF ITS PRESUMPTIVE CONCLUSION.II.
THE HONORABLE COURT OF APPEALS ERRED IN APPLYING THE PRINCIPLE OF RES IPSA LOQUITOR (sic) WHEN THE DEFENSE WAS ABLE TO PROVE THAT THERE IS NO NEGLIGENCE ON THE PART OF THE PETITIONER, AND NO OVERDOSING IN THE APPLICATION OF THE ANESTHETIC AGENT BECAUSE THERE WAS NO 100% HALOTHANE ADMINISTERED TO THE CHILD, BUT ONLY ONE (1%) PERCENT AND THE APPLICATION THEREOF, WAS REGULATED BY AN ANESTHESIA MACHINE. THUS, THE APPLICATION OF THE PRINCIPLE OF RES IPSA LOQUITOR (sic) CONTRADICTED THE ESTABLISHED FACTS AND THE LAW APPLICABLE IN THE CASE.III.
THE AWARD OF MORAL DAMAGES AND EXEMPLARY DAMAGES IS NOT JUSTIFIED THERE BEING NO NEGLIGENCE ON THE PART OF THE PETITIONER. ASSUMING THAT THE CHILD IS ENTITLED TO FINANCIAL CONSIDERATION, IT SHOULD BE ONLY AS A FINANCIAL ASSISTANCE, BECAUSE THERE WAS NO NEGLIGENCE, AND NO OVERDOSING OF ANESTHETIC AGENT AND AS SUCH, THE AWARD IS SO EXCESSIVE, AND NO FACTUAL AND LEGAL BASIS.[23]
Medical malpractice cases do not escape the application of this doctrine. Thus, res ipsa loquitur has been applied when the circumstances attendant upon the harm are themselves of such a character as to justify an inference of negligence as the cause of that harm. The application of res ipsa loquitur in medical negligence cases presents a question of law since it is a judicial function to determine whether a certain set of circumstances does, as a matter of law, permit a given inference.
Although generally, expert medical testimony is relied upon in malpractice suits to prove that a physician has done a negligent act or that he has deviated from the standard medical procedure, when the doctrine of res ipsa loquitur is availed by the plaintiff, the need for expert medical testimony is dispensed with because the injury itself provides the proof of negligence. The reason is that the general rule on the necessity of expert testimony applies only to such matters clearly within the domain of medical science, and not to matters that are within the common knowledge of mankind which may be testified to by anyone familiar with the facts. Ordinarily, only physicians and surgeons of skill and experience are competent to testify as to whether a patient has been treated or operated upon with a reasonable degree of skill and care. However, testimony as to the statements and acts of physicians and surgeons, external appearances, and manifest conditions which are observable by any one may be given by non-expert witnesses. Hence, in cases where the res ipsa loquitur is applicable, the court is permitted to find a physician negligent upon proper proof of injury to the patient, without the aid of expert testimony, where the court from its fund of common knowledge can determine the proper standard of care. Where common knowledge and experience teach that a resulting injury would not have occurred to the patient if due care had been exercised, an inference of negligence may be drawn giving rise to an application of the doctrine of res ipsa loquitur without medical evidence, which is ordinarily required to show not only what occurred but how and why it occurred. When the doctrine is appropriate, all that the patient must do is prove a nexus between the particular act or omission complained of and the injury sustained while under the custody and management of the defendant without need to produce expert medical testimony to establish the standard of care. Resort to res ipsa loquitur is allowed because there is no other way, under usual and ordinary conditions, by which the patient can obtain redress for injury suffered by him.
Thus, courts of other jurisdictions have applied the doctrine in the following situations: leaving of a foreign object in the body of the patient after an operation, injuries sustained on a healthy part of the body which was not under, or in the area, of treatment, removal of the wrong part of the body when another part was intended, knocking out a tooth while a patient’s jaw was under anesthetic for the removal of his tonsils, and loss of an eye while the patient plaintiff was under the influence of anesthetic, during or following an operation for appendicitis, among others.
Nevertheless, despite the fact that the scope of res ipsa loquitur has been measurably enlarged, it does not automatically apply to all cases of medical negligence as to mechanically shift the burden of proof to the defendant to show that he is not guilty of the ascribed negligence. Res ipsa loquitur is not a rigid or ordinary doctrine to be perfunctorily used but a rule to be cautiously applied, depending upon the circumstances of each case. It is generally restricted to situations in malpractice cases where a layman is able to say, as a matter of common knowledge and observation, that the consequences of professional care were not as such as would ordinarily have followed if due care had been exercised. A distinction must be made between the failure to secure results, and the occurrence of something more unusual and not ordinarily found if the service or treatment rendered followed the usual procedure of those skilled in that particular practice. It must be conceded that the doctrine of res ipsa loquitur can have no application in a suit against a physician or surgeon which involves the merits of a diagnosis or of a scientific treatment. The physician or surgeon is not required at his peril to explain why any particular diagnosis was not correct, or why any particular scientific treatment did not produce the desired result. Thus, res ipsa loquitur is not available in a malpractice suit if the only showing is that the desired result of an operation or treatment was not accomplished. The real question, therefore, is whether or not in the process of the operation any extraordinary incident or unusual event outside of the routine performance occurred which is beyond the regular scope of customary professional activity in such operations, which, if unexplained would themselves reasonably speak to the average man as the negligent cause or causes of the untoward consequence. If there was such extraneous intervention, the doctrine of res ipsa loquitur may be utilized and the defendant is called upon to explain the matter, by evidence of exculpation, if he could.
On January 7, 1973, Dr. Brigham admitted 15-year-old Randall Swanson to a hospital for the treatment of infectious mononucleosis. The patient's symptoms had included a swollen throat and some breathing difficulty. Early in the morning of January 9 the patient was restless, and at 1:30 a.m. Dr. Brigham examined the patient. His inspection of the patient's air passage revealed that it was in satisfactory condition. At 4:15 a.m. Dr. Brigham received a telephone call from the hospital, advising him that the patient was having respiratory difficulty. The doctor ordered that oxygen be administered and he prepared to leave for the hospital. Ten minutes later, 4:25 a.m., the hospital called a second time to advise the doctor that the patient was not responding. The doctor ordered that a medicine be administered, and he departed for the hospital. When he arrived, the physician who had been on call at the hospital had begun attempts to revive the patient. Dr. Brigham joined him in the effort, but the patient died.
The doctor who performed the autopsy concluded that the patient died between 4:25 a.m. and 4:30 a.m. of asphyxia, as a result of a sudden, acute closing of the air passage. He also found that the air passage had been adequate to maintain life up to 2 or 3 minutes prior to death. He did not know what caused the air passage to suddenly close.
x x x x
It is a rare occurrence when someone admitted to a hospital for the treatment of infectious mononucleosis dies of asphyxiation. But that is not sufficient to invoke res ipsa loquitur. The fact that the injury rarely occurs does not in itself prove that the injury was probably caused by someone's negligence. Mason v. Ellsworth, 3 Wn. App. 298, 474 P.2d 909 (1970). Nor is a bad result by itself enough to warrant the application of the doctrine. Nelson v. Murphy, 42 Wn.2d 737, 258 P.2d 472 (1953). See 2 S. Speiser, The Negligence Case – Res Ipsa Loquitur § 24:10 (1972). The evidence presented is insufficient to establish the first element necessary for application of res ipsa loquitur doctrine. The acute closing of the patient’s air passage and his resultant asphyxiation took place over a very short period of time. Under these circumstances it would not be reasonable to infer that the physician was negligent. There was no palpably negligent act. The common experience of mankind does not suggest that death would not be expected without negligence. And there is no expert medical testimony to create an inference that negligence caused the injury.
On the witness stand, Dr. Vertido made a significant turnaround. He affirmed the findings and conclusions in his report except for an observation which, to all intents and purposes, has become the storm center of this dispute. He wanted to correct one piece of information regarding the dosage of the anesthetic agent administered to the child. He declared that he made a mistake in reporting a 100% halothane and said that based on the records it should have been 100% oxygen.
The records he was relying on, as he explains, are the following:
(a) the anesthesia record – A portion of the chart in the record was marked as Exhibit 1-A and 1-B to indicate the administration at intervals of the anesthetic agent.
(b) the clinical abstract – A portion of this record that reads as follows was marked Exhibit 3A. 3B – Approximately 1 hour and 45 minutes through the operation, patient was noted to have bradycardia (CR = 70) and ATSO4 0.2 mg was immediately administered. However, the bradycardia persisted, the inhalational agent was shut off, and the patient was ventilated with 100% oxygen and another dose of ATSO4 0.2 mg was given. However, the patient did not respond until no cardiac rate can be auscultated and the surgeons were immediately told to stop the operation. The patient was put on a supine position and CPR was initiated. Patient was given 1 amp of epinephrine initially while continuously doing cardiac massage – still with no cardiac rate appreciated; another ampule of epinephrine was given and after 45 secs, patient’s vital signs returned to normal. The entire resuscitation lasted approximately 3-5 mins. The surgeons were then told to proceed to the closure and the child’s vital signs throughout and until the end of surgery were: BP = 110/70; CR = 116/min and RR = 20-22 cycles/min (on assisted ventilation).
Dr. Vertido points to the crucial passage in the clinical abstract that the patient was ventilated with 100% oxygen and another dose of ATSO4 when the bradycardia persisted, but for one reason or another, he read it as 100% halothane. He was asked to read the anesthesia record on the percentage of the dosage indicated, but he could only sheepishly note I can’t understand the number. There are no clues in the clinical abstract on the quantity of the anesthetic agent used. It only contains the information that the anesthetic plan was to put the patient under general anesthesia using a nonrebreathing system with halothane as the sole anesthetic agent and that 1 hour and 45 minutes after the operation began, bradycardia occurred after which the inhalational agent was shut off and the patient administered with 100% oxygen. It would be apparent that the 100% oxygen that Dr. Vertido said should be read in lieu of 100% halothane was the pure oxygen introduced after something went amiss in the operation and the halothane itself was reduced or shut off.
The key question remains – what was the quantity of halothane used before bradycardia set in?
The implication of Dr. Vertido’s admission is that there was no overdose of the anesthetic agent, and the accused Dr. Solidum stakes his liberty and reputation on this conclusion. He made the assurance that he gave his patient the utmost medical care, never leaving the operating room except for a few minutes to answer the call of nature but leaving behind the other members of his team Drs. Abella and Razon to monitor the operation. He insisted that he administered only a point 1% not 100% halothane, receiving corroboration from Dr. Abella whose initial MA in the record should be enough to show that she assisted in the operation and was therefore conversant of the things that happened. She revealed that they were using a machine that closely monitored the concentration of the agent during the operation.
But most compelling is Dr. Solidum’s interpretation of the anesthesia record itself, as he takes the bull by the horns, so to speak. In his affidavit, he says, reading from the record, that the quantity of halothane used in the operation is one percent (1%) delivered at time intervals of 15 minutes. He studiedly mentions – the concentration of halothane as reflected in the anesthesia record (Annex D of the complaint-affidavit) is only one percent (1%) – The numbers indicated in 15 minute increments for halothane is an indication that only 1% halothane is being delivered to the patient Gerard Gercayo for his entire operation; The amount of halothane delivered in this case which is only one percent cannot be summated because halothane is constantly being rapidly eliminated by the body during the entire operation.
x x x x
In finding the accused guilty, despite these explanations, the RTC argued that the volte-face of Dr. Vertido on the question of the dosage of the anesthetic used on the child would not really validate the non-guilt of the anesthesiologist. Led to agree that the halothane used was not 100% as initially believed, he was nonetheless unaware of the implications of the change in his testimony. The court observed that Dr. Vertido had described the condition of the child as hypoxia which is deprivation of oxygen, a diagnosis supported by the results of the CT Scan. All the symptoms attributed to a failing central nervous system such as stupor, loss of consciousness, decrease in heart rate, loss of usual acuity and abnormal motor function, are manifestations of this condition or syndrome. But why would there be deprivation of oxygen if 100% oxygen to 1% halothane was used? Ultimately, to the court, whether oxygen or halothane was the object of mistake, the detrimental effects of the operation are incontestable, and they can only be led to one conclusion – if the application of anesthesia was really closely monitored, the event could not have happened.[34]
Whether or not a physician has committed an “inexcusable lack of precaution” in the treatment of his patient is to be determined according to the standard of care observed by other members of the profession in good standing under similar circumstances bearing in mind the advanced state of the profession at the time of treatment or the present state of medical science. In the recent case of Leonila Garcia-Rueda v. Wilfred L. Pacasio, et. al., this Court stated that in accepting a case, a doctor in effect represents that, having the needed training and skill possessed by physicians and surgeons practicing in the same field, he will employ such training, care and skill in the treatment of his patients. He therefore has a duty to use at least the same level of care that any other reasonably competent doctor would use to treat a condition under the same circumstances. It is in this aspect of medical malpractice that expert testimony is essential to establish not only the standard of care of the profession but also that the physician's conduct in the treatment and care falls below such standard. Further, inasmuch as the causes of the injuries involved in malpractice actions are determinable only in the light of scientific knowledge, it has been recognized that expert testimony is usually necessary to support the conclusion as to causation.
x x x x
In litigations involving medical negligence, the plaintiff has the burden of establishing appellant's negligence and for a reasonable conclusion of negligence, there must be proof of breach of duty on the part of the surgeon as well as a causal connection of such breach and the resulting death of his patient. In Chan Lugay v. St Luke's Hospital, Inc., where the attending physician was absolved of liability for the death of the complainant’s wife and newborn baby, this Court held that:“In order that there may be a recovery for an injury, however, it must be shown that the ‘injury for which recovery is sought must be the legitimate consequence of the wrong done; the connection between the negligence and the injury must be a direct and natural sequence of events, unbroken by intervening efficient causes.’ In other words, the negligence must be the proximate cause of the injury. For, ‘negligence, no matter in what it consists, cannot create a right of action unless it is the proximate cause of the injury complained of.’ And ‘the proximate cause of an injury is that cause, which, in natural and continuous sequence, unbroken by any efficient intervening cause, produces the injury, and without which the result would not have occurred.’”
Presented for review by this committee is the case of a 3 year old male who underwent a pull-thru operation and was administered general anesthesia by a team of anesthesia residents. The patient, at the time when the surgeons was manipulating the recto-sigmoid and pulling it down in preparation for the anastomosis, had bradycardia. The anesthesiologists, sensing that the cause thereof was the triggering of the vago-vagal reflex, administered atropine to block it but despite the administration of the drug in two doses, cardiac arrest ensued. As the records show, prompt resuscitative measures were administered and spontaneous cardiac function re-established in less than five (5) minutes and that oxygen was continuously being administered throughout, unfortunately, as later become manifest, patient suffered permanent irreversible brain damage.
In view of the actuations of the anaesthesiologists and the administration of anaesthesia, the committee find that the same were all in accordance with the universally accepted standards of medical care and there is no evidence of any fault or negligence on the part of the anaesthesiologists.
FISCAL CABARON Doctor, what do you mean by General Anesthetic Agent? WITNESS General Anesthetic Agent is a substance used in the conduction of Anesthesia and in this case, halothane was used as a sole anesthetic agent. x x x x QNow under paragraph two of page 1 of your report you mentioned that after one hour and 45 minutes after the operation, the patient experienced a bradycardia or slowing of heart rate, now as a doctor, would you be able to tell this Honorable Court as to what cause of the slowing of heart rate as to Gerald Gercayo?
WITNESS Well honestly sir, I cannot give you the reason why there was a bradycardia of time because is some reason one way or another that might caused bradycardia. FISCAL CABARON What could be the possible reason? A Well bradycardia can be caused by anesthetic agent itself and that is a possibility, we’re talking about possibility here. Q What other possibility do you have in mind, doctor? A Well, because it was an operation, anything can happen within that situation. FISCAL CABARON Now, this representation would like to ask you about the slowing of heart rate, now what is the immediate cause of the slowing of the heart rate of a person? WITNESS Well, one of the more practical reason why there is slowing of the heart rate is when you do a vagal reflex in the neck wherein the vagal receptors are located at the lateral part of the neck, when you press that, you produce the slowing of the heart rate that produce bradycardia. Q I am pro[p]ounding to you another question doctor, what about the deficiency in the supply of oxygen by the patient, would that also cause the slowing of the heart rate? A Well that is a possibility sir, I mean not as slowing of the heart rate, if there is a hypoxia or there is a low oxygen level in the blood, the normal thing for the heart is to pump or to do not a bradycardia but a … to counter act the Hypoxia that is being experienced by the patient (sic). x x x x Q Now, you made mention also doctor that the use of general anesthesia using 100% halothane and other anesthetic medications probably were contributory to the production of hypoxia. A Yes, sir in general sir.[41]
ATTY. COMIA I noticed in, may I see your report Doctor, page 3, will you kindly read to this Honorable court your last paragraph and if you will affirm that as if it is correct? A “The use of General Anesthesia, that is using 100% Halothane probably will be contributory to the production of Hypoxia and - - - -” ATTY COMIA And do you affirm the figure you mentioned in this Court Doctor? WITNESS Based on the records, I know the - - - Q 100%? A 100% based on the records. Q I will show you doctor a clinical record. I am a lawyer I am not a doctor but will you kindly look at this and tell me where is 100%, the word “one hundred” or 1-0-0, will you kindly look at this Doctor, this Xerox copy if you can show to this Honorable Court and even to this representation the word “one hundred” or 1-0-0 and then call me. x x x x ATTY. COMIA Doctor tell this Honorable Court where is that 100, 1-0-0 and if there is, you just call me and even the attention of the Presiding Judge of this Court. Okay, you read one by one. WITNESS Well, are you only asking 100%, sir? ATTY. COMIA I’m asking you, just answer my question, did you see there 100% and 100 figures, tell me, yes or no? WITNESS I’m trying to look at the 100%, there is no 100% there sir. ATTY. COMIAOkay, that was good, so you Honor please, may we request also temporarily, because this is just a xerox copy presented by the fiscal, that the percentage here that the Halothane administered by Dr. Solidum to the patient is 1% only so may we request that this portion, temporarily your Honor, we are marking this anesthesia record as our Exhibit 1 and then this 1% Halothane also be bracketed and the same be marked as our Exhibit “1-A”.
x x x x ATTY. COMIA Doctor, my attention was called also when you said that there are so many factors that contributed to Hypoxia is that correct? WITNESS Yes, sir. QI remember doctor, according to you there are so many factors that contributed to what you call hypoxia and according to you, when this Gerald suffered hypoxia, there are other factors that might lead to this Hypoxia at the time of this operation is that correct?
WITNESS The possibility is there, sir. Q And according to you, it might also be the result of such other, some or it might be due to operations being conducted by the doctor at the time when the operation is being done might also contribute to that hypoxia is that correct? A That is a possibility also. x x x x ATTY. COMIA How will you classify now the operation conducted to this Gerald, Doctor? WITNESS Well, that is a major operation sir. Q In other words, when you say major operation conducted to this Gerald, there is a possibility that this Gerald might [be] exposed to some risk is that correct? AThat is a possibility sir.
Q And which according to you that Gerald suffered hypoxia is that correct? A Yes, sir. Q And that is one of the risk of that major operation is that correct? A That is the risk sir.[42]
x x x is a doubt growing reasonably out of evidence or the lack of it. It is not a captious doubt; not a doubt engendered merely by sympathy for the unfortunate position of the defendant, or a dislike to accept the responsibility of convicting a fellow man. If, having weighed the evidence on both sides, you reach the conclusion that the defendant is guilty, to that degree of certainty as would lead you to act on the faith of it in the most important and crucial affairs of your life, you may properly convict him. Proof beyond reasonable doubt is not proof to a mathematical demonstration. It is not proof beyond the possibility of mistake.