witness testimony under Fed. R.Civ.P. 37(c)(1), which states in pertinent part: A party that without substantial justification fails to disclose information required by Rule 26(a) ... is not, unless such failure is harmless, permitted to use as evidence at a trial, at a hearing or on a motion any witness or information not so disclosed. This circuit has established that Rule 37(c)(1) mandates that a trial court sanction a party for discovery violations in connection with Rule 26(a) unless the violations were harmless or were substantially justified. Plaintiff has not demonstrated that his failure to abide by Rule 26(a) was either harmless or justified. See Knoll v. A.T.T. Co., 176 F.3d 359, 363 (6th Cir.1999); Salgado v. General Motors Corp., 150 F.3d 735, 742 n. 6 (7th Cir.1998) (<HOLDING>); Ames v. Van Dyne, No. 95-3376, 1996 WL 662899
holding that a violation of the hearsay rule was harmless holding that rule 37c1 puts teeth into rule 26 and that the district court acted well within its discretion when it decided to impose the sanction of precluding the witnesses from testifying since the sanction of exclusion is automatic and mandatory unless the sanctioned party can show that its violation of rule 26a was either justified or harmless holding rule 11 sanction proceeding was exempt from automatic stay recognizing that the decision whether to sanction a party and if so the severity of such sanction is vested in the sound discretion of the trial court holding that a trial court had the authority to impose a default judgment as a sanction for violating a rule 16 scheduling order pursuant to rule 37b2 stating we agree with the basic premise that a default sanction can under certain circumstances be an appropriate response to a violation of a rule 16 order after all the express terms of rule 37 permit a trial court to impose sanctions when a party fails to obey an order to provide or permit discovery