Below is a comprehensive discussion of the Subpoena under Rule 21 of the Rules of Court in the Philippines (with references to related rules, relevant jurisprudence, ethical considerations, and practical pointers). The discussion is organized as follows:

Definition and Nature
Forms of Subpoena
By Whom Issued
Form and Contents
Service of Subpoena
Duty to Appear; Personal Appearance in Court
Grounds for Quashal or Modification
Subpoena for Depositions
Failure to Comply and Sanctions (Contempt)
Ethical Considerations
Sample Legal Forms

1. Definition and Nature

A subpoena is a process directed to a person requiring that person:
1. To attend and testify at a hearing, trial, or any investigation conducted by competent authority; or
2. To bring any books, documents, or other things under his/her control, in which case it is termed subpoena duces tecum.
The issuance of a subpoena is part of the court’s (or other authorized officer’s) authority to compel attendance or production of evidence necessary to resolve a dispute or conduct an inquiry.
Its main function is to aid in the orderly administration of justice by ensuring the availability of witnesses and documentary evidence.

2. Forms of Subpoena

a. Subpoena Ad Testificandum

A subpoena ad testificandum compels the person to appear and testify as a witness in a hearing or trial.

b. Subpoena Duces Tecum

A subpoena duces tecum compels the person to produce documents, papers, books, accounts, letters, photographs, or other tangible items relevant to a proceeding.
It may also include the command to testify, but its primary function is the production of evidence.

3. By Whom Issued

Under Section 2, Rule 21 of the Rules of Court, the following persons have authority to issue a subpoena:

The Court in which the witness is required to attend;
The Court of the place where the deposition is to be taken;
The officer or body authorized by law to do so in connection with investigations, such as administrative bodies, quasi-judicial agencies, and commissioners delegated to take depositions or testimonies.

4. Form and Contents

a. Contents of a Subpoena Ad Testificandum

The title of the case;
The court, body, or officer where the witness is required to appear;
The specific date, time, and place where the witness must attend;
A statement that failure to comply may be punished by contempt.

b. Contents of a Subpoena Duces Tecum

In addition to the above, a subpoena duces tecum must:

Adequately describe the documents or things to be produced;
Show the materiality or relevance of those documents/things to the issues of the case;
Not be unreasonable or oppressive in scope.

c. Particularity and Certainty

A subpoena duces tecum must specify with particularity the documents, papers, or objects sought to be produced, so that the person subpoenaed may know what is required and so the court can determine their relevancy.

d. Notice of Consequences for Non-Compliance

The subpoena should contain a notice that failure to comply without lawful excuse will be dealt with as indirect contempt of court.

5. Service of Subpoena

a. Manner of Service

Service of a subpoena is done personally by handing a copy of the subpoena to the person being subpoenaed or, if they refuse to receive it, by tendering it to them.
The service must be made within a reasonable time before the date fixed for attendance to allow the witness or the person subpoenaed to adequately prepare.

b. Proof of Service

The server (usually a sheriff or other authorized process server) must submit a return indicating the manner, place, and date of service and any pertinent observations about the service (e.g., whether the person refused to receive the subpoena).

c. Tender of Fees and Expenses

Witness fees and reasonable traveling expenses must be tendered to the person subpoenaed. Absent such fees, the service of subpoena may be considered defective, and non-compliance may be excused.
For ordinary witnesses, the amount is governed by applicable regulations (often minimal), but for expert witnesses, special considerations on reasonable expert fees may apply.

6. Duty to Appear; Personal Appearance in Court

Once a witness or a party is validly served with a subpoena ad testificandum, he/she is generally obligated to appear at the specified place and time.
However, the court may dispense with the personal appearance of the witness if the person subpoenaed is:
1. Outside the territorial jurisdiction of the issuing court (unless the subpoena is for a deposition or the person consents);
2. Physically unable to appear due to serious illness or other justifiable reasons;
3. The testimony is already available by deposition or other modes of discovery, and the court deems personal appearance unnecessary.

7. Grounds for Quashal or Modification

Under Section 4, Rule 21, a subpoena may be quashed (cancelled) or modified upon motion promptly made if:

Unreasonable and oppressive – The subpoena is too broad, unduly burdensome, or does not specify the documents with sufficient particularity.
Irrelevant or not material – The documents or testimony sought are not relevant to the issues in the case, or are of such a nature that they do not help in the resolution of the dispute.
Witness is not bound – The subpoena requires a person to appear who is not legally obligated to do so (e.g., lack of personal jurisdiction over the witness or the witness is beyond 100 kilometers, subject to certain exceptions).
Violation of a legal privilege or confidentiality – If compliance would breach privileged communications (e.g., attorney-client privilege, doctor-patient privilege, or executive privilege), the subpoena may be quashed.

A motion to quash or modify should be filed before the time specified for compliance. If the court finds partial validity (e.g., some documents sought are relevant, while others are not), it may modify the subpoena accordingly.

8. Subpoena for Depositions

A subpoena may be issued under Rule 23 (Depositions Pending Action), Rule 24 (Depositions Before Action), or Rule 25 (Depositions Upon Written Interrogatories) of the Rules of Court to compel:
1. The appearance of a deponent; and/or
2. The production of documents in the deponent’s possession or control.
The rules on quashal or modification also apply to a subpoena for depositions.
If the subpoena is for the taking of depositions, it is generally issued by the court where the case is pending or by the court of the place where the deposition is to be taken.

9. Failure to Comply and Sanctions (Contempt)

a. Contempt of Court

Failure to obey a subpoena without adequate cause is punishable as indirect contempt.
The court may issue a show-cause order requiring the non-complying person to explain why he/she should not be held in contempt.

b. Possible Penalties

Depending on the gravity of the disobedience, the court may impose:
1. A fine;
2. Imprisonment; or
3. Both fine and imprisonment.

c. Remedies

A person unjustly cited for contempt may seek remedies such as a motion for reconsideration or a petition for certiorari, depending on the circumstances of the case.

10. Ethical Considerations

a. Lawyers’ Duties in Issuing or Requesting Subpoena

Candor and Good Faith: Lawyers must ensure that subpoenas are requested only when the testimony or documents sought are truly relevant and material to the case.
Avoidance of Harassment: Rule 10.03 of the Code of Professional Responsibility (CPR) states that a lawyer shall observe fairness and avoid tactics that tend to harass witnesses. Requesting subpoenas for irrelevant documents or to unduly burden a witness can be unethical.
Respect for Privileged Information: Lawyers should not seek to subpoena privileged communications unless there is a legal ground to pierce the privilege, and they must respect confidentiality of certain records (e.g., medical, bank records, if not otherwise permitted by law or by the court).

b. Officers of the Court

Judges and quasi-judicial officers must ensure that subpoenas are not abused and do not become instruments of oppression. They have an ethical duty to protect people from unreasonable or harassing subpoenas.

c. Responsibility of the Lawyer Regarding Fees

The lawyer who causes the issuance of the subpoena must see to it that reasonable witness fees and travel expenses are tendered. This is both a procedural requirement and an ethical one, to avoid compelling attendance without just compensation.

11. Sample Legal Forms

Below are simplified examples of forms for a subpoena ad testificandum and subpoena duces tecum under the Philippine Rules of Court. They are for illustration purposes only and may be adapted to conform with local court practice, letterhead, or formatting requirements.

A. Sample Form: Subpoena Ad Testificandum

Republic of the Philippines
REGIONAL TRIAL COURT
[Branch Number], [City/Province]

PEOPLE OF THE PHILIPPINES,   |    Criminal Case No. [ ]
   Plaintiff,                |
                             |
       - versus -            |
                             |
[NAME OF ACCUSED],           |
   Accused.                  |
______________________________________

                                  SUBPOENA
TO: [Name of Witness]
    [Address]

GREETINGS:

You are hereby commanded to appear and testify as a witness at [Specify: the trial/hearing] in the above-entitled case on [Date], at [Time], in the Session Hall of this Court located at [Court Address].

In case of failure to appear without lawful excuse, you may be held in contempt of court, punishable by fine or imprisonment or both.

WITNESS the signature of the Honorable Presiding Judge this [Day] day of [Month, Year] at [City/Province].

                        (Seal of the Court)

                        _____________________________
                        [Name of Judge]
                        Presiding Judge

B. Sample Form: Subpoena Duces Tecum

Republic of the Philippines
REGIONAL TRIAL COURT
[Branch Number], [City/Province]

[PLAINTIFF],               |   Civil Case No. [ ]
   Plaintiff,              |
                           |
       - versus -          |
                           |
[DEFENDANT],               |
   Defendant.              |
______________________________________

                             SUBPOENA DUCES TECUM
TO: [Name of Witness/Custodian of Records]
    [Position/Office/Address]

GREETINGS:

You are hereby commanded to appear before this Court on [Date] at [Time] and bring with you the following documents, to wit:

1. [Enumerate specific documents, e.g., “All original payroll records of XYZ Corporation for the period January 2024 to December 2024.”]  
2. [Any other specific materials relevant to the case.]

These documents are required as evidence in the above-entitled case, and your failure to comply without lawful excuse may subject you to punishment for contempt.

WITNESS the signature of the Honorable Presiding Judge this [Day] day of [Month, Year] at [City/Province].

                        (Seal of the Court)

                        _____________________________
                        [Name of Judge]
                        Presiding Judge

Note: If witness fees are required by law or the Rules, the appropriate amount must be tendered at the time of service.

Key Takeaways

A subpoena is an essential process for compelling the attendance of witnesses and the production of material evidence.
It must be issued by a court or other competent authority and served personally, with reasonable fees and mileage tendered.
The subpoena must be reasonable in scope, relevant to the case, and not unduly oppressive or burdensome.
Non-compliance without lawful reason can lead to contempt.
Lawyers must ensure that subpoenas are used ethically—only to secure necessary evidence and never as a tool for harassment.

In sum, Rule 21 on Subpoena is a critical component of Philippine civil procedure (as well as criminal and administrative proceedings), ensuring that courts and duly authorized bodies can enforce compulsory process over witnesses and documents. Proper understanding and observance of these rules—together with ethical standards—promote the efficient and fair administration of justice.