Should a witness for trial ignore your subpoena, the only avenue to compel obedience is by making an application pursuant to CPLR 2308. Failure to comply with the subpoena is treated as a contempt of court.
The judicial subpoena is a crucial tool for any lawyer seeking to ensure the attendance at trial of a witness not under their control. CPLR 2303 details the proper method of service for a judicial subpoena. CPLR 2303 & 8001 require a witness fee be provided a reasonable time in advance of the trial, in the amount of $15 dollars for each day’s attendance and $0.23 in travel expenses for each mile traveled (covering the distance from the place served to the Courthouse). Travel expenses are not required where the witness is travelling wholly within a city (including travel within New York City). If the witness is a non-party, they are entitled to an additional $3 ($18 plus travel expenses). Absent this payment in advance, the subpoena is not enforceable. Once provided a firm trial date by the Court, make sure you have subpoenaed any witness you expect to call other than your own client and expert. It is good practice to include on the subpoena and cover letter a request that the witness contact you prior to appearing, to aid in scheduling and dealing with last minute adjournments of the trial date. If you plan to call the opposing party as a witness, you may serve the party’s attorney of record rather than the defendant himself under CPLR 2303-a. The subpoena for an opposing party should instruct the witness to contact their own attorney (instruction to contact you is a violation of the attorney no-contact rule).
Should a witness for trial ignore your subpoena, the only avenue to compel obedience is by making an application pursuant to CPLR 2308. Failure to comply with the subpoena is treated as a contempt of court. The trial court will have broad discretion to fashion a remedy. CPLR §2308(a) explicitly permits the Court to issue a warrant directing the sheriff to bring the witness to the courthouse. The importance of the witness to proving your case will be a factor considered by the judge in determining whether a warrant will be issued. Where the non-compliant witness is a party to the action, the Court is more likely to fashion a more severe remedy, including an adverse inference or striking the opposing parties pleadings. When faced with a situation where a subpoenaed witness fails to appear at trial, good practice dictates you request on the record that the trial judge issue a warrant directing the sheriff to compel the witness to appear, and a continuance through the date of that appearance.  Be sure to have proof of service at the time of the application.
The best way to mitigate the risk of a crucial witness ignoring your subpoena is performing their deposition prior to the time of trial. Under CPLR 3117(a)(3)(iv), you may read the deposition of a non-party for any purpose, provided you can establish that you were unable to procure their attendance despite diligent “efforts.” Should you properly subpoena a witness who fails to appear, you may argue to the trial court in good faith that you have satisfied this requirement. Although there is a dearth of Appellate Division and Court of Appeals case law on whether a subpoena alone is sufficient to satisfy the “diligent efforts” requirement, at least one lower court has held that it does not. In Miller v. Daub, 128 Misc. 2d 1060, 492 N.Y.S.2d 703 (N.Y. Civ. Ct. July 29, 1985), New York City Civil Court Judge David B. Saxe held that the deposition of a nonparty witness may only be read into evidence after reasonable attempts to compel enforcement of the subpoena, as discussed in the preceding paragraph, have been made. As such, it is best practice to depose and subpoena all witnesses you wish to testify at trial, and immediately make an application to enforce that subpoena should the witness fail to appear. Should all the foregoing fail to produce the witness, a request to read the witnesses deposition testimony, under CPLR 3117(a)(3)(iv), must be made.
 Hernandez v Mueller, 29 Misc. 3d 522 *, 907 N.Y.S.2d 583, 2010 N.Y. Misc. LEXIS 3780, 2010 NY Slip Op 20321, 244 N.Y.L.J. 38 (N.Y. Sup. Ct., Kings, 2010)(“as a nonparty subpoenaed to give testimony at an examination before trial, he was entitled to a witness fee of $ 18, not $ 15. The difference is not de minimis.”)
 Brown v. Eimicke, 144 A.D.2d 460, 461, 533 N.Y.S.2d 1015, 1015, 1988 N.Y. App. Div. LEXIS 11789, *2 (N.Y. App. Div. 2d Dep’t 1988)(“The proper procedure for compelling obedience to a subpoena is an application pursuant to CPLR 2308”)
 Hefte v. Bellin, 137 A.D.2d 406, 408, 524 N.Y.S.2d 42, 44, 1988 N.Y. App. Div. LEXIS 792, *5 (N.Y. App. Div. 1st Dep’t 1988)(“While CPLR 2308 (a) leaves the decision whether to issue a warrant for a witness to the discretion of the court, where a witness’ testimony is not only relevant but necessary to a party’s case, a warrant should issue when that witness does not respond to a judicial subpoena”).
 Simplicity Pattern Co. v. Miami Tru-Color Off-Set Serv., 210 A.D.2d 24 *, 619 N.Y.S.2d 29, 1994 N.Y. App. Div. LEXIS 11830 (N.Y. App. Div. 1st Dep’t 1994)(“an adverse inference could be drawn against Miami Tru-Color for its failure to produce its president at trial”)
 Papoutsis v. NOV Trans. Corp., 309 A.D.2d 841 *, 766 N.Y.S.2d 52, 2003 N.Y. App. Div. LEXIS 10895 (N.Y. App. Div. 2d Dep’t 2003)(where subpoenaed police officer failed to appear to lay a foundation for the police accident report, counsel called the process server as a witness and established proper service, requesting a continuance to secure police officer as a witness. 2nd Department overturned the trial courts denial of a continuance to allow time to secure the officer’s compliance)
 See generally, Collins v 7-11 Corp., 146 A.D.3d 931, 45 N.Y.S.3d 536, (2d Dep’t, Jan. 25, 2017)
 Miller v. Daub, 128 Misc. 2d 1060, 492 N.Y.S.2d 703 (N.Y. Civ. Ct. July 29, 1985)