delivered the opinion of the court:
Plaintiff Beverly Ashford brought an action pursuant to the Paternity Act (Ill. Rev. Stat. 1979, ch. 40, par. 1351 et seq.) to have defendant William Ziemann declared to be the father of her daughter, born September 5, 1978.1 Following a jury verdict of nonpaternity, *36plaintiff appeals, contending that: (1) the trial court erred in refusing to admit the daughter’s birth certificate into evidence; (2) the trial court should have excluded the testimony of one of the defense witnesses; (3) remarks made by defense counsel in closing argument were so prejudicial as to require reversal; and (4) the verdict was against the manifest weight of the evidence.
Plaintiff Beverly Ashford and defendant William Ziemann have known each other since 1965. Both parties agree that during the early years of their relationship they dated steadily and had sexual relations frequently. During the 1970’s the parties saw each other sporadically. Plaintiff had not seen defendant for some time when, on December 10, 1977, she and her roommate were walking down the street on their way to buy a Christmas tree and saw defendant coming out of an alley in his car. Plaintiff testified that defendant offered to help them get the tree but said that he had to go to work first. Defendant, a detective for the Chicago police department, said that he would take the two women home, check into work, and return to take them shopping later. Defendant came to plaintiff’s apartment that evening in an unmarked police car and took the two women to buy a tree. After bringing the tree back to plaintiff’s apartment, plaintiff and defendant went out for a drink and then to defendant’s apartment. Defendant left plaintiff there while he returned to work to check out. When he returned, they had intercourse “a couple of times” before going to sleep, and again in the morning. Plaintiff testified that the parties engaged in sexual intercourse on December 17, 1977, and on January 20, 1978, and also on New Year’s Eve, December 31, 1977, each time at defendant’s apartment. It was on New Year’s Eve that plaintiff first told defendant that she thought she was pregnant. During January of 1978, the parties also had dinner at plaintiff’s apartment twice. On both occasions defendant was on duty as a police officer. Plaintiff’s roommate testified that she was present during those dinners and at some of the times when defendant picked plaintiff up to take her to his apartment. After January 1978, the parties did not communicate for several months. In the summer of 1978, plaintiff called defendant to discuss their responsibilities to the unborn child. Defendant told her that the child was not his responsibility and that she should get a lawyer.
Plaintiff also testified that her last menstrual period was on November 28, 1977, and that she had not dated anyone except defendant since 1976.
Defendant testified that he dated plaintiff between 1965 and 1969 and that after they stopped dating they maintained a friendly rela*37tionship. He stated that he did help plaintiff and her roommate with their Christmas tree in early December of 1977, but could not recall the exact date and stated that they picked up the tree in his personal car and he did not take plaintiff to his apartment that day. Defendant also testified that plaintiff was at his apartment on one occasion, which may have been New Year’s Eve, and he drove her home late that night. Defendant denied having intercourse with plaintiff during December of 1977 or January of 1978. Defendant went to plaintiff’s apartment several times in early 1978 to help her with her car. He stated that they had discussed her pregnancy and that she implied that he was the father of the child. Defendant testified that plaintiff had talked about marriage often in the late 1960’s, and once had asked him if he would marry her if he was still single when he was 35.
James Storz was the only other witness called by the defense. His existence was revealed to plaintiff’s counsel during the jury conference after the bulk of plaintiff’s case in chief had been presented. He was first interviewed by defense counsel during trial and was deposed by plaintiff’s counsel the day before he was called as a witness. Storz testified that he is a bartender who has worked in several taverns in plaintiff’s neighborhood. He first met plaintiff in the summer of 1977 while he was working. Between then and November of 1977, he encountered plaintiff several times and they had drinks together each time. During the weekend before Thanksgiving 1977, he met plaintiff at a bar where they stayed for several hours. They then went to his apartment where they had intercourse. He met plaintiff by chance in the neighborhood twice during December of 1977, and on one of these occasions they went to his apartment and had intercourse. Storz met plaintiff again in January of 1978. She told him that she was pregnant and they discussed an abortion and the possibility of giving the baby up for adoption. Plaintiff rejected both suggestions. Storz did not see plaintiff again until the trial. On cross-examination, Storz was asked to describe plaintiff. He stated that she was five feet six inches tall, weighed 150 pounds and has brown eyes, “shapely” legs, and no scars or identifying marks. He also stated that she drank scotch and water or scotch on the rocks.
Plaintiff testified as a rebuttal witness. She stated that she had never seen Storz before he walked into the courtroom. She also said that she is five feet two inches tall, weighs 105 pounds, has blue eyes, has noticeable scars and birthmarks and that one of her legs is shorter and thinner than the other as a result of childhood polio. She also stated that she drinks nothing but beer or spritzer and that she *38did not frequent the bars where Storz claimed to have met her.
I
We first consider plaintiff’s contention that the trial court erred in refusing to admit the daughter’s birth certificate into evidence. A certificate of live birth of plaintiff’s daughter signed by Stuart Abel, M.D., was received by the Chicago department of health on September 15, 1978. The birth certificate listed the child’s name, date and time of birth, sex, and place of birth. The certificate also listed the name, address, age, and place of birth of plaintiff, the mother. The certificate contained the age (37) and place of birth (Illinois) of the father, but the father’s name was not included, in accordance with section 12(4) of the Vital Records Act (Ill. Rev. Stat. 1981, ch. lll1^, par. 73 — 12(4)), which states:
“(4) If the mother was not married to the father of the child either at the time of conception or birth, the name of the father shall not be entered on the certificate of birth without the written consent of the mother and the person to be named as the father unless a determination of paternity has been made by a court of competent jurisdiction, in which case the name of the father as determined by the court shall be entered.”
Plaintiff, who signed the live birth certificate, identified a certified copy of it during her testimony in her case in chief. Also in plaintiff’s case in chief, defendant was called as an adverse witness and asked his date of birth and place of birth. Plaintiff then sought admission of the birth certificate into evidence. Upon defendant’s objection, the trial court denied admission, stating:
“In this case, my ruling is that it will be denied. The law is very clear that you cannot insert the name of the alleged father without his consent. I am not going to permit by innuendo now that she put the defendant on the stand and identified him as being age 37 and living in the City of Chicago. That’s my ruling.”
We believe that the birth certificate constituted relevant and proper evidence, and that the trial court erred in refusing its admission. An essential element of a paternity case is proof of a “child born out of wedlock.” (Ill. Rev. Stat. 1981, ch. 40, par. 1351 et seq.) This birth certificate, with the father’s name not entered, was probative of the fact that a child was born out of wedlock. Thus, the birth certificate was relevant evidence.
We next address the potential hearsay objection to the birth certificate, and find it not valid for two reasons. Initially, we *39conclude that the certificate was not hearsay, because the oút-of-court declarations were those of plaintiff and she testified at trial and was subject to cross-examination by the defendant against whom the exhibit is offered. (People v. Carpenter (1963), 28 Ill. 2d 116, 120-22, 190 N.E.2d 738.) This case is not a situation in which an attempt is made to introduce testimony by a third person, nor is there any issue of the remoteness of the declaration; rather, we are dealing with a certificate of live birth signed by the plaintiff who testified and was subject to cross-examination. (See People v. Osborn (1977), 53 Ill. App. 3d 312, 319, 368 N.E.2d 608; People v. Clark (1972), 52 Ill. 2d 374, 388-89, 288 N.E.2d 363; 2 Gard, Illinois Evidence Manual sec. 14.09, at 72- 73 (2d ed. 1979).) Alternatively, if the birth certificate was hearsay, it was admissible because of the exception to the hearsay rule for records of vital statistics. Fed. R. Evid. 803(9); McCormick, Evidence sec. 316, at 736 (2d ed. 1972); Cleary & Graham, Handbook of Illinois Evidence sec. 803.14, at 450 (3d ed. 1979).
It might also be noted that this relevant evidence corroborates plaintiff’s testimony as a prior consistent statement. By contesting the paternity action, defendant challenges the veracity of plaintiff’s testimony. Under such circumstance, the evidence is admissible. See Cleary & Graham, Handbook of Illinois Evidence sec. 611.14, at 319-20 (3d ed. 1979); McCormick, Evidence sec. 251, at 604 (2d ed. 1972); 2 Gard, Illinois Evidence Manual sec. 14.09, at 71 (2d ed. 1979); Fed. R. Evid. 801; People v. Clark (1972), 52 Ill. 2d 374, 382; People v. Rosario (1978), 65 Ill. App. 3d 170, 174, 382 N.E.2d 31.
The trial court apparently excluded the birth certificate because of prejudice to defendant. We disagree and find that any prejudice to defendant is outweighed by the probative value of the birth certificate. Of course in any paternity action, there may be evidence prejudicial to the defendant. If we understand the trial court, it might never be possible to complete a birth certificate pursuant to section 12(4) of the Vital Records Act (Ill. Rev. Stat. 1981, ch. lllVa, par. 73— 12(4)). That plaintiff listed the age of the father as 37 and his place of birth as Illinois at the time of completing the certificate in September 1978 is probative in this paternity action.
II
We next consider plaintiff’s contention that the trial court erred in refusing to exclude James Storz from testifying as a sanction for defendant’s violation of the discovery rules. On January 31, 1979, plaintiff propounded a set of interrogatories to defendant, which included a request for disclosure of the existence of any other men that *40defendant contended had intercourse with plaintiff. Despite the filing by plaintiff of two motions to compel the answer of these interrogatories, defendant never filed an answer.
On January 13, 1981, plaintiff moved to set the case for trial, alleging that discovery was complete. On Monday, March 9, 1981, the date scheduled to commence trial, defendant requested a continuance until the next day. On March 10, at the start of the trial, defendant told the court that he would have one or two witnesses. At the conclusion of the proceedings on that date, defendant advised the court he would put defendant on the stand plus one more witness. On Wednesday, March 11, before trial commenced, defendant advised the court and plaintiff about James Storz. Apparently the notification took place in the court’s chambers out of the presence of a court reporter.2 Based upon the record before us the following facts emerge: (1) the court said defendant’s counsel stated he did not know anything about this witness until a week ago (March 4); (2) defendant’s counsel said Storz came to his attention some time last week, maybe Friday (March 6), maybe Saturday (March 7); and (3) Storz testified on March 12 and said he first became aware of the case about 10 days ago on a Sunday evening (March 1). Based upon any reasonable interpretation of the record, it is obvious defendant became aware of Storz at the earliest on March 1 and at the latest on March 7. In any respect, it was prior to March 9, the date scheduled for trial when defendant requested a one-day continuance, yet for some unexplained reason, the surprise witness Storz was not announced until March ll.3
The trial court overruled plaintiff’s objection to permitting Storz to testify, but permitted the plaintiff to depose Storz during a lunch break. There is no record that plaintiff sought a continuance because of the disclosure of this surprise witness.
Supreme Court Rule 219(c) (iv) (87 Ill. 2d R. 219(c)(iv)) permits the exclusion of a witness for unreasonable failure to comply with discovery requests. The determination of whether a witness should be excluded is within the sound exercise of the trial court’s de*41cisión. (Kirkwood v. Checker Taxi Co. (1973), 12 Ill. App. 3d 129, 133, 298 N.E.2d 233.) The factors to be considered in determining whether exclusion is proper are: “the surprise to the adverse party, the prejudicial effect of the testimony, the nature of the testimony, the diligence of the adverse party, the timely objection to the testimony and the good faith of the party calling the witness.” 12 Ill. App. 3d 129, 132.
In our opinion, the record clearly established that defendant wilfully violated the supreme court rules governing discovery. We therefore conclude that the trial court abused its discretion in refusing to bar the testimony of Storz. It is apparent that defendant knew of the existence of this witness for several days before disclosure to plaintiff. Due to the explosive impact that this witness’ testimony had on plaintiff’s case, time for investigation might have substantially aided plaintiff. For the same reason, late disclosure worked to defendant’s advantage.
The dissent states that “the trial court’s field of discretion in the employment of this sanction is narrowly circumscribed. (See Mason v. Mundelein Lanes, Inc. (1979), 72 Ill. App. 3d 990, 993-94, 391 N.E.2d 151; Smith v. Realcoa Construction Co. (1973), 13 Ill. App. 3d 254, 259, 300 N.E.2d 855.)” In Mason, the excluded witness was first named as a potential witness early in 1975, over two years before trial. In Smith, defendant was permitted to call as witness a person not listed on defendant’s answers to interrogatories. However, plaintiffs were aware that the witness was on the job while they were also employed on the job. We think these cases are inapposite.
We realize that plaintiff’s counsel failed to protect plaintiff’s interests to the fullest extent possible by failure to insist on answers to the interrogatories and failure to move for a continuance once the surprise witness was presented. We cannot, however, find a waiver in this lack of diligence by counsel in light of the deliberate concealment of a material witness by defendant. Accordingly, we hold that the trial court abused its discretion in refusing to impose the sanction of barring the testimony of Storz.
III
The errors of the circuit court in failing to exclude Storz as a witness and in denying admission of the birth certificate into evidence warrant reversal and a remand for a new trial. Accordingly, we find it unnecessary to reach the other two issues raised by plaintiff. These issues are not likely to arise on remand.
The judgment of the circuit court is reversed, and this cause is re*42manded for further proceedings consistent with this opinion.
Reversed and remanded.
HARTMAN, J., concurs.