Policy Text
JACKIE LACEY
DISTRICT ATTORNEY LOS ANGELES COUNTY DISTRICT ATTORNEY’S OFFICE
ONEMINUTE
BRIEF
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NUMBER : 2020-23 DATE : 07-23-20 BY: Devallis Rutledge TOPIC : Reasonable Suspicion & PC
ISSUE : How does “reasonable suspicion ” differ from “probable cause? ”
● Different degrees of official interference with a person ’s Fourth Amendment liberty or
privacy interests are justified by correspondingly different levels of informat ion.
• Detentions and pat searches must be just ified by reasonable sus picion that the
person is involved in criminal activity (detentions) , or is armed and dangerous (pat-
downs) . Terry v. Ohio (1968) 392 US 1, 22.
• Arrests and searche s must be jus tified by probable cause that the person has
committed a crime ( arres ts), or that contraband or the fruits, instrumentalities or evidence
of a crime will be found in the place to be searched with a warrant, or that one of the
recogn ized exceptions applies (searches) . Katz v. US (1967) 389 US 347, 357.
● What do “reasonable s uspicion” and “proba ble cause ” mean? The Supreme Court
does not define them :
“Articulating precisely what ‘reasonable suspicion ’ and ‘probable cause ’ mean is not
possible. They are commonsense, nontechnical conceptions that deal wi th the fac tual and
practical considerat ions of everyday life on which reasonabl e and prudent men, not legal
technicians, act. As such, the standards are not readily , or even usefully , reduced to a neat
set of legal rules. ” Ornelas v. US (1996) 517 US 690, 695.
● But without attempting to define the terms, the Supreme Court has contrasted them:
“Reasonable suspicion is a less demanding standard than probable c ause , not
only in the sense that reasonable susp icion can be established with information that is
differ ent in quantity or content than that required to establish probable cause, but also in the
This information was current as of publication date. It is not intended as legal advice. It is
recommended that readers check for subsequent developments, and consult legal advisors to ensure
currency after publication. Loc al policies and procedures r egar ding application should be observed.
LADA ONE -MINUTE BRIEF NO. 2020-23 PAGE 2
sense that reasonable suspicion can arise from information that is less reliable than that
requi red to show probable cause. ” Alabama v. White (1990) 496 US 325, 330.
“A determination that reasonable suspicion exists … need not rule out the possibility
of innocent conduct. ” US v. Arvizu (2002) 534 US 266, 277. And “[Reasonable] suspicion is
considerably less than proof of wrongdoing by a preponderance of the evidence. ” US v.
Sokolow (1989) 490 US 1, 7.
“The Fourth Amendment does not require a policem an who lacks the precise level of
information necessary for p robable cause to arrest to simply shrug his shoulders and allow a
crime to occur or a criminal to escape. … A brief stop of a suspicious individual, in order to
determine his identity or to maintain the status quo momentarily while obtaining more
informati on, may be most reasonable in light of the facts known to the officer at the t ime.”
Adams v. Williams (1972) 4 07 US 143, 145 -46.
● Example : An officer on night p atrol sees a car ahead of him in traffic with no running
lights on, weaving somewhat in the lane . Is this reasonable suspicion to make a detention
for suspected DUI? Yes. Arburn v. DMV (2007) 151 Cal.App. 4th 1480, 1485 . But would the
officer immediately arrest the stopped driver ? Not likely.
Further investigation might reveal slu rred speech, strong odor of alcohol, poor FST
performance and admission to having been drinking. These additional facts , added t o the
driving , would es tablish probable cause for arrest . (On the other hand, if investigation had
revealed that a sober driver in a ren ted car was inattentive to his lane as he fumbled to find
the light switch in an unfamiliar vehicle, there would be neither p robable cause nor a DUI
arrest—though the stop would still be good .)
BOTTOM LINE : Simply s tated, “reasonable suspicion ” is a lower level of suspicion ,
based on less information , of a less reliable nature, than probable cause; and
conversely, “probable ca use” is a greater suspic ion, based on more information , of a
more reliable nature, than reasonable suspicion.
(Emphases added and punctuation and citations omitted in quoted material.)