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Guide to Data Source Mapping

Identify potentially relevant data sources, assess deletion risks and build a practical preservation plan before gaps become costly problems.

What is Data Source Mapping?

Data source mapping is a process that creates a working record of the systems, accounts, devices and repositories that may contain information relevant to a dispute.

Be defensible

If preservation decisions are ever challenged, a documented map showing what was identified, who owned it, and what was done demonstrates a reasonable, good-faith process.

Reduce risk

Flagging retention settings and deletion risks up front means your team isn't caught out by information being purged before it could be preserved.

Create accountability

Naming a responsible person per source and requiring confirmation of action closes the "I assumed someone else handled it" gap, which is often where preservation failures actually happen.

Avoid problems further down the line

Missing a source early can create a bigger issue later on and could mean additional collections, repeated interviews, unexpected review costs or gaps in the available evidence.

For matters governed by Practice Direction 57AD in the Business and Property Courts of England and Wales, the duties include:

Preserve

Take reasonable steps to preserve potentially relevant documents within a party's control.

Suspend

Suspend all relevant deletion processes.

Prevent

Take reasonable steps to prevent agents or third parties holding documents on its behalf from destroying them.

Look beyond email and shared drives

The right sources depend on the matter and how the people involved actually worked. Here are the categories you should check:

Communications: email, calendars, Teams, Slack, SMS, WhatsApp and other business messaging tools.
Documents and collaboration: laptops, shared drives, SharePoint, OneDrive, Google Drive, document management systems and paper records.
Business systems: finance, HR, CRM, ERP, customer support, project management and other specialist platforms.
Meetings and mobile data: recordings, transcripts, meeting chats, voicemails and device or app records.
Historical sources: former employee accounts, archives, retired systems and backups.
External sources: consultants, outsourced providers and other organisations holding relevant information.

Map the problem, not the app

In Microsoft Teams, for example, a retention policy covering messages won't automatically cover the files used within it. Recordings and transcripts need the same scrutiny, remember to check storage locations and retention settings.

AI tools deserve the same treatment, were they used in work relevant to the dispute? Ask whether prompts, responses, generated documents and the underlying source material exist and can be preserved. Microsoft's Copilot guidance sets out specific retention and eDiscovery capabilities, along with limitations that vary by feature and configuration.

A practical six-step approach

This practical six-step approach gives you valuable, real-world insight into each stage of the data source mapping journey. For over two decades our experts have supported legal teams in mapping data sources in a way that ensures defensibility. We're experts in the data, so that you can be experts in the courtroom.

Step 1: Define your matter's scope

Start with the dispute: which events, transactions or decisions are relevant?

What time period needs to be considered? Which people, teams and business functions were involved? Where might information supporting or undermining either party's position be found?

This keeps the exercise focused. A company-wide system inventory can provide a starting point, but it needs to be connected to the facts of the matter.

Step 2: Identify urgent preservation risks

Find out whether potentially relevant information is exposed to automatic deletion, disappearing messages, device replacement, employee departure or system decommissioning. Assign urgent actions as these risks emerge. Never wait for every source to be identified before addressing a known threat to relevant data.

Step 3: Speak to the people who know the work

Bring together legal, IT, records management and the relevant business teams.

IT can explain the organisation's systems and controls.
Business users can explain where discussions took place, which shared workspaces they used and whether important records sit outside the expected repositories.

Ask specific questions: "Where did the team discuss changes to the contract?" will usually reveal more than "Which systems do you use?" Include former employees and external providers where relevant, and record any access or ownership questions that need legal assessment.

Step 4: Build a map that drives action

For each potentially relevant source, always record:

identity and location
relevance and coverage
ownership and access
retention and risk
preservation action
status and verification

Keep this in a controlled working document with a named owner. An unknown retention setting should appear as an unresolved action, rather than an empty cell that everyone assumes someone else will address.

Step 5: Confirm that preservation works

A hold notice or completed task is a starting point for verification. Ask the technical team to confirm that the preservation measure covers the relevant accounts, locations, content types and dates.

Where collection is needed, establish whether the method retains the metadata, attachments, version history and conversation context needed to interpret the records and treat backups as a source to assess. Establish what they contain, how they rotate and whether they can support the preservation required. And make sure to record limitations and escalate gaps quickly.

Step 6: Review the map as the matter develops

Update the map when new custodians or issues emerge, employees leave, systems change or collections reveal another source.

Keep preservation, collection and disclosure decisions distinct. Identifying a source does not mean every item must be collected immediately or ultimately disclosed.

Equally, deciding against immediate collection does not resolve whether potentially relevant material should be preserved. Record decisions about sources, their rationale and any circumstances that would require reconsideration.

What does an actionable entry look like?

Imagine two companies are in a legal dispute, and some of the evidence lives in a Microsoft Teams channel and a linked SharePoint folder. If you're responsible for preserving that evidence, just writing "Teams - relevant" as your note isn't good enough because it doesn't tell anyone what to do.

A useful entry note should cover the following points:

Which channel and folder are involved

Which people and what date ranges matter

How long messages and files are kept

Warnings that accounts are about to close

Who is responsible for preservation

Updates around the preservation

Our support helps you identify priorities early

Understanding how to map data sources can often feel overwhelming, but our experts can help guide and support you from the very beginning.

We offer free, no-obligation disclosure strategy sessions to help legal teams identify priorities and establish practical next steps.