Licensed Private Investigators · Chicago
Greyline is a licensed investigation agency staffed by former law-enforcement and intelligence professionals. We work quietly, document everything, and bring back answers that hold up.
Investigation Services
Personal or corporate, simple or complex — every assignment is handled by a licensed investigator and documented for whatever comes next, including court.
Covert, lawful observation with time-stamped photo and video — establishing patterns, activity, and the facts you need.
Deep, lawful due diligence on people and businesses — history, records, affiliations, and red flags before you commit.
Sensitive personal matters handled with discretion and care — clear evidence so you can stop wondering and decide.
Internal theft, fraud, due diligence, and asset checks — protecting your business with quiet, defensible investigation.
Why Greyline
Our investigators come from law enforcement, military intelligence, and corporate security. We know how to gather facts the right way — quietly, legally, and in a form that stands up to scrutiny.
20+ yrs
Field experience per lead
2,400+
Cases closed
100%
Confidential intake
In Confidence
“They gave me clarity I'd been chasing for months — documented, professional, and handled so discreetly no one ever knew.”
Personal Matter · Referred by counsel
“We suspected internal theft but had nothing solid. Greyline built the case quietly and we resolved it without a public mess.”
Business Owner · Corporate case
“Their report held up where it counted. Thorough, lawful, and exactly what our attorney needed.”
Litigation Support · Cook County