Evidence Grounding

Evidence grounding is a core safety property of MARCUS. The system is designed to answer from selected project material and to show that material back to the user for review.

Grounding is what turns MARCUS from a general-purpose text generator into a library-based evidence assistant.

Current data boundary: Grounding does not make MARCUS a PHI workspace. Do not enter patient identifiers, patient-specific clinical facts, PHI, credentials, secrets, or other prohibited data.

What Grounded Means In MARCUS

A cited answer is assembled from selected passages in the permitted question scope, with citations that point back to those passages or their parent sources.

In practical terms, that means:

• the answer should be tied to your uploaded evidence
• the user should be able to inspect that evidence
• the answer should reflect the limits of the available library

Grounding is not the same thing as certainty. It is the discipline of tying claims back to visible support.

What Grounding Protects Against

Grounding reduces the risk of:

• unsupported claims presented as if they came from your documents
• drift into general background knowledge when the task is supposed to be project-specific
• answers that sound polished but cannot be audited

It does not eliminate all failure modes, but it makes them more visible and more manageable.

What Grounding Does Not Guarantee

Grounding does not guarantee:

• that the project contains the complete evidence base
• that the highest-authority source was uploaded
• that conflicting sources have been resolved automatically
• that the cited source is the right fit for every clinical or operational circumstance
• that the answer is complete just because it is cited

This is why MARCUS still expects user judgment.

The Boundary Between Supported And Unsupported

Grounded output can have different levels of visible support:

• well supported: the answer is clearly backed by relevant, authoritative citations
• partially supported: the answer has some evidence, but the library is thin or the citations are narrow
• weakly supported: the evidence exists but is limited, low-authority, or only loosely connected
• unsupported for this library: the permitted source set does not contain enough evidence for a reliable answer

These descriptions are review categories, not calibrated probabilities.

How MARCUS Handles Uncertainty

When evidence is sparse or weak, MARCUS should trend toward:

• visibly limited coverage or support
• narrower, more qualified answers
• clearer citation dependency

If the indexed documents do not support the question, MARCUS is designed to return an insufficient-evidence response. Check the scope or add an approved missing source rather than trying to force a stronger-sounding synthesis.

Why Coverage Matters

Coverage is not exactly the same as correctness. Coverage is about whether the library seems to contain enough relevant evidence for the question asked.

That means:

• a correct-looking answer with limited coverage still deserves caution
• a high-authority source with limited coverage may still leave important gaps
• broader selected support can make an answer easier to review, but does not prove completeness or correctness

Coverage is a navigation and review cue, not a probability or certification.

Why Authority Matters

Source evidence labels identify document type, publication information, version status and metadata origins. They help you inspect the source without reducing its quality to one number.

A document-type classification does not ratify a source or decide which local policy controls. Confirm version, issuer, approval, and applicability directly.

Local Applicability Matters Too

An answer can be well grounded in the wrong kind of source for your use case.

Examples:

• a general guideline may be authoritative but not the controlling local workflow
• a local policy may be operationally controlling even if it is not the strongest general evidence source
• an educational note may describe the topic well but still be the wrong basis for a live decision

This is why grounding should always be interpreted with context, not treated as a magic stamp of correctness.

How Users Should Read A Cited Answer

When an answer matters, ask:

1. Do the citations actually support the main claim?
2. Are the sources strong enough for this decision?
3. Is the answer drawing from the right kind of source, not just any source?
4. Does the library appear complete enough for the question?
5. If sources disagree, is that conflict visible or hidden?

This is the practical discipline of evidence-grounded use.

When To Open The Citations Immediately

Open the citations when:

• the answer turns on a threshold
• two sources might conflict
• the question affects escalation, discharge, medication, or another high-stakes decision
• the answer sounds stronger than you expected
• coverage is low or the source quality is unclear

In MARCUS, opening citations is not a sign of distrust. It is the normal completion of the workflow.

Common Misunderstandings About Grounding

The Core User Responsibility

MARCUS is built to make source review faster, not optional. The user's job is not to distrust every answer reflexively. The user's job is to use citations, source evidence, and coverage cues to judge how strongly the available source set supports the conclusion.

One Practical Summary

Grounding means MARCUS should show its evidence. Safe use means you still read that evidence when the decision matters.

Continue

• Clinician handbook: Questions, Answers, and Citations
• Safety: Safe Use and Limitations