(General information only; not legal advice.)

1) The basic idea: a “new arrest” can exist even if the person is already jailed

In Philippine practice, a detainee may be physically in custody (already behind bars) yet still need to be placed under arrest for a different offense in a legal sense—because each criminal case requires its own lawful basis for detention.

That lawful basis is typically one of the following:

a warrant of arrest issued by a court;
a warrantless arrest under the Rules of Court (e.g., in flagrante delicto); or
a commitment order (mittimus/commitment) or comparable court order recognizing that the accused is already detained and should remain so for the newly filed case.

A person already detained for Case A cannot be kept indefinitely for Case B unless Case B has its own legal foundation (warrant/commitment). Conversely, if Case A is dismissed or bail is approved and posted, the detainee must be released unless there is a valid separate hold for Case B.

2) Principal legal sources and doctrines that govern the situation

A. Constitution (Bill of Rights) Key guardrails apply even inside a jail:

Due process and the requirement of probable cause for warrants.
Right to counsel and rights during custodial investigation.
Protection against unreasonable searches (modified by the realities of jail security).
Rights against torture, coercion, or secret detention.

B. Rules of Court

Rule 113 (Arrest): when arrests require warrants and when warrantless arrests are allowed (in flagrante, hot pursuit, escapee).
Rule 112 (Preliminary investigation / inquest framework): how prosecutors proceed after warrantless arrest and how courts act upon filing of information.
Rule 114 (Bail): bail eligibility, conditions, cancellation, and the effect of new charges.

C. Revised Penal Code (RPC) and related penal laws Two sets of liabilities matter:

The detainee’s new offense (e.g., assault, possession of contraband, escape attempt).
Potential liabilities of officers for unlawful detention practices (e.g., arbitrary detention, delay in delivery to judicial authorities), plus administrative accountability.

D. Rights statutes that frequently arise in detention incidents

The statute on rights of persons arrested/detained under custodial investigation (commonly invoked for counsel and warnings).
The Anti-Torture law and related rules (especially when force is used after a jail incident).

3) Two different “new crime” scenarios—very different arrest rules

When someone already in custody is implicated in a new crime, the law’s approach depends heavily on when and how the new crime is discovered.

Scenario 1: The detainee commits a new crime inside custody (often witnessed)

Examples: assaulting a guard, stabbing another detainee, possessing drugs or a weapon found during an inspection, destroying jail property, inciting riot, attempting escape.

Core concept: Jail personnel (or responding officers) can treat this as a warrantless arrest in flagrante delicto if the act is committed in their presence or its commission is directly perceived.

Even though the person is already physically detained, the law still expects:

notice of the cause of arrest,
documentation, and
prompt referral to the prosecutor for inquest or filing.

Scenario 2: The “new crime” was committed outside custody (or not witnessed) and only discovered later

Example: while detained for theft, investigators later find probable cause linking the detainee to a separate robbery weeks earlier; or a new complainant files a case; or a warrant is issued in another city.

Core concept: This usually does not qualify for a new warrantless arrest (no in flagrante/hot pursuit). The proper route is:

complaint → preliminary investigation (or appropriate prosecutorial action) → information → court action (warrant or commitment order acknowledging existing detention).

4) Is a warrant required when the person is already in jail?

General rule: Arrests are made by virtue of a warrant. Exceptions: Warrantless arrests are allowed only in the specific instances set by the Rules of Court (in flagrante, hot pursuit, escapee).

But once the accused is already detained, courts and jail authorities often proceed through a practical/legal substitute:

The court may issue a commitment order or an order recognizing that the accused is already under detention and should be held for the new case (rather than “physically arresting” again).

Important distinction:

A “warrant” is about taking custody.
A “commitment order” is about continuing/maintaining custody under a case’s authority. Both are used to ensure the detention is legally supported for the newly filed charge.

5) How “service of a warrant” works on someone already detained

If a court issues a warrant of arrest for Case B and the accused is already in jail for Case A, service typically looks like this:

The warrant is served at the detention facility.
The detainee is informed of the warrant and the cause.
Jail records reflect that the detainee is now held under multiple legal bases (multiple commitments/warrants).

This “service” matters because it anchors:

lawful continued detention if Case A ends, and
scheduling of arraignment and other proceedings in Case B.

6) Prosecutor pathway: inquest vs. preliminary investigation

A. Inquest (common when the new offense happens inside jail and is “caught in the act”)

If the new offense is treated as a warrantless arrest event, prosecutors commonly proceed by inquest (a summary determination of probable cause for filing an information in court).

Key practical points:

The incident report, sworn statements, medical reports, and seized items become the backbone of probable cause.
Time sensitivity is high because of potential officer liability for delay in presenting the arrested person to judicial authorities for the new offense (even if the person is already physically detained).

B. Preliminary investigation (common when the new offense is not in flagrante or is an older outside offense)

If the new offense is not a proper warrantless-arrest case, the normal route is preliminary investigation:

Complaint-affidavit and supporting evidence are filed.
The respondent is given the chance to submit counter-affidavits.
The prosecutor resolves probable cause; if found, an information is filed in court.
The court then acts (warrant or commitment order for an accused already in custody).

7) Article 125 (delay in delivery) and the “already detained” complication

Philippine penal law penalizes officers who delay bringing an arrested person to judicial authorities (with time periods often discussed in practice based on the gravity of the offense).

When the person is already detained, the temptation is to treat the new crime as administratively “internal.” That is risky. For a new warrantless-arrest situation (e.g., in flagrante inside the jail), authorities still need to act promptly to bring the matter to the prosecutor/court process for Case B.

The safer operational approach is to assume that the clock for the new offense is treated seriously and to move quickly with:

booking/incident documentation,
immediate referral for inquest, and
prompt filing.

8) Custodial investigation rules apply even more inside a jail

A detainee is already in a coercive environment. Any questioning about a new crime is classic custodial investigation territory.

Key consequences:

The detainee must be informed of the right to remain silent and to counsel.
Counsel must be competent and independent; waivers must meet strict standards.
Confessions obtained without compliance risk being inadmissible.
Coercion or force can create criminal, administrative, and evidentiary consequences.

9) Jail searches and contraband discoveries: security vs. admissibility

Detention facilities conduct searches for safety—cell inspections, strip searches when justified, contraband sweeps. Compared to free society, detainees have a reduced expectation of privacy, but searches should still be reasonable and consistent with security needs and facility rules.

Common legal flashpoints:

Whether the search was a legitimate security measure or a pretext to gather evidence.
Chain of custody and documentation for seized drugs/weapons.
Whether alleged contraband “found in a common area” can be attributed to a particular detainee without corroboration.

10) Paperwork that makes or breaks legality: warrants, commitments, and “detainers”

To prevent unlawful detention disputes and operational chaos, jails typically require paper authority per case.

Common controlling documents include:

Commitment order / mittimus (for detention under a case or after conviction).
Warrant of arrest (for taking custody or placing the accused under arrest for that case).
Order to produce (so the detainee can attend inquest, arraignment, hearings, trial).
Release order (for ending detention under a case).
Hold/Detainer (practice varies; it should be anchored on an actual pending case, warrant, or court order—not merely an informal request).

Critical rule of thumb: A detainee should not remain in custody “because another case might be filed.” There must be a concrete legal basis—filed case, warrant/commitment, or an order.

11) Bail complications when a new crime arises during custody

A. If the detainee is on bail for Case A (or could be granted bail) and commits Case B

New criminal conduct can trigger bail cancellation or forfeiture processes in Case A if it violates bail conditions or indicates flight risk (implementation depends on the court).
Case B will have its own bail analysis, which may be stricter if the new offense is serious.

B. If the detainee posts bail in Case A Release is proper unless there is an existing lawful basis to hold the person for Case B (warrant/commitment). This is where failure to secure Case B paperwork leads to improper detention claims.

12) The “already convicted” prisoner: special consequences (quasi-recidivism and prison discipline)

If the person is not merely a pre-trial detainee but a convict serving sentence, a new felony committed during service of sentence can trigger quasi-recidivism under the RPC, which generally results in the penalty for the new felony being imposed in its maximum period.

Separately, correctional institutions impose administrative discipline (loss of privileges, segregation, etc.), which is distinct from criminal prosecution and does not replace it.

13) Typical “new crimes in custody” and legal characterization issues

Common charges arising inside detention include:

Direct assault / resistance and disobedience (if the victim is a person in authority or agent).
Physical injuries / homicide / murder (depending on harm and circumstances).
Possession of dangerous drugs and related offenses (often hinging on chain of custody).
Possession of deadly weapons (depending on applicable penal statutes and facility regulations).
Escape-related offenses (depending on status as detainee vs. convict and the manner of escape/attempt).
Damage to property, threats, coercion.
Bribery/corruption-related offenses (sometimes involving visitors or personnel).

Charging decisions depend on the detainee’s status (pre-trial vs. convict), the victim’s status (e.g., jail officer), and the evidence quality.

14) Court logistics: producing the detainee for inquest, arraignment, and hearings

Because the detainee is already confined, courts typically issue orders directing jail authorities to produce the detainee for:

inquest proceedings (when required),
arraignment,
pre-trial,
trial, and
promulgation of judgment.

Failure to properly produce can delay proceedings and create rights issues (speedy trial concerns), but movement must be balanced with security.

15) Rights and remedies: what can go wrong and what follows

A. For law enforcement / jail personnel

Potential exposures include:

Arbitrary detention (keeping someone without valid legal ground for Case B).
Delay liabilities (failure to promptly bring the new warrantless arrest into the judicial process).
Evidence suppression (inadmissible confessions, defective chain of custody).
Administrative sanctions for procedural breaches.
Criminal liability under anti-torture and other penal statutes if force/coercion is used unlawfully.

B. For the detainee/accused

Consequences include:

additional criminal prosecution,
denial or tightening of bail conditions,
aggravating treatment in sentencing if already serving sentence (quasi-recidivism), and
administrative discipline within the facility.

C. For victims and witnesses inside jail

Protection concerns are acute. Witness intimidation is common in closed environments; documentation, medical examinations, and prompt prosecutorial action are decisive.

16) Operational checklists (Philippine practice-oriented)

A. When a new crime occurs inside the jail (caught in the act)

Secure the scene; render medical aid.
Separate participants; preserve evidence.
Document the incident (incident report; sworn statements; CCTV extraction if any).
Properly seize and inventory contraband (chain of custody discipline).
Ensure rights advisories before any questioning; counsel if interrogation occurs.
Refer promptly for inquest/complaint filing; coordinate with prosecutor.
Ensure the court issues the correct warrant/commitment for the new case to support continued detention.

B. When the new crime is an older outside offense discovered while detainee is already held

File complaint and proceed with preliminary investigation.
Upon filing of information, obtain court action (warrant or commitment order).
Serve the warrant/commitment at the jail; update detention records.
Secure orders to produce for arraignment and hearings.

C. Before releasing a detainee (because Case A ended or bail posted)

Confirm whether there is any active warrant/commitment for Case B (or other cases).
Do not rely on informal “requests” without legal papers.
Release only when no valid detention authority remains.

17) Bottom line

A detainee can be “arrested” for a new crime while already in custody, but Philippine law still demands a proper legal basis per case, strict respect for custodial rights, and prompt movement into the prosecutor-and-court process—especially when the new offense is treated as a warrantless arrest situation inside the detention facility.