Click to e-mail any question

Sources of Probable Cause

The basic thrust of the law in this area is that there are some sources of probable cause that need to be supplemented by other sources, and then, there are some sources that are good enough by themselves. There's no need to adhere to a totality of circumstances test, or checklist format (e.g., 4 out of 10 possible sources equals probable cause). The law makes ample use of precedents set in other areas of procedural and evidence law.

Most of the sources can be categorized into four (4) groups:

• Observation -- These are things that the police officer obtains knowledge of via the senses: sight, smell, hearing; but this category would also include the kinds of inferences to be made when the experienced police officer is able to detect a familiar pattern (of criminal activity) that contains a series of suspicious behaviors (e.g., circling the block twice around an armored car unloading at a bank).

• Expertise -- These are the kinds of things that a police officer is specially trained at; such things as gang awareness and identification, recognition of burglar tools, the ability to read graffitti and tatoos, and various other techniques in the general direction of knowing when certain gestures, movements, or preparations tend to indicate impending criminal activity.

• Circumstantial Evidence -- This is evidence that points the finger away from other suspects or an alibi, and by a process of elimination, the only probable conclusion to be drawn is that the person or things left behind is involved in crime.

• Information -- This is a broad category which includes informants, statements by witnesses and victims, and announcements via police bulletins, broadcasts, and at roll call.

• Direct Sources of Probable Cause (Officer sources of knowledge)

  FLIGHT -- Attempting to flee, evade or elude, is in evidence law a presumption of guilt. It's not by itself sufficient for probable cause, but it's surely going to result in a chase situation and custodial detention of some sort. The case of Wong Sun v. U.S. (1963) covered suspects who run out the side or back door as sufficient for probable cause, however, and there have been other cases in which suspicious behavior like dropping packages or using phones but not talking have held up.

  FURTIVE MOVEMENTS -- "Furtive" means secretive or concealing, and the law requires a totality of circumstances here. The movement cannot possibly be construed as an innocent gesture (looking both ways before crossing the street). Nervousness alone is not sufficient as the law recognizes the right of people to be nervous or fearful around police. The movement cannot also be possibly the sign of a mental condition. There must be something secretive given the time, setting, weather, and audience. It would be best if the furtive movements were identifiable with a particular type of crime.

  OBSERVATION OF REAL EVIDENCE -- "Real" evidence is demonstrative evidence (Exhibit A) that speaks for itself. Most of the time, these kinds of things are in plain view (binoculars and cameras are allowed as well as normal extensions of the senses, but you can't use a portable microscope to analyze the grass for fibers, e.g.). Fresh footprints is a good example, and the list includes: imprints, impressions, models, diagrams, sketches, photographs, video, and computer animation.

  ADMITTED OWNERSHIP -- This involves, for example, a type of consent in which a person, say, accidentally empties the contents of their purse or pockets, and the police ask them if they own something, and they say "yes", and then the police look inside it and find contraband, they are said to have had probable cause for the search and seizure.

  FALSE OR IMPROBABLE ANSWERS -- This is not normally a basis of probable cause alone, but it tends to trigger subsequent police inquiry or action. Examples might include a person being asked who the car belongs to, and they say "my cousin" but they don't know their cousin's name. Or, a girlfriend answers the door and says the apartment is rented under her boyfriend's name, but she doesn't know what kind of car her boyfriend drives.

  PRESENCE AT A CRIME SCENE or IN A HIGH-CRIME AREA -- The two of these are actually somewhat different. Police have more powers at crime scenes to commandeer something, but in high-crime areas, this source of probable cause is definitely not sufficient by itself, and would probably be an example of nullification under the void-for-vagueness doctrine applicable to loitering. There are a couple of rules, however. The "joint possession" rule means that everyone in the house is subject to search and seizure if the drugs and/or contraband are in a prominent location. The totality of circumstances test applies in high-crime areas where (a) the neighborhood has to have a notorious reputation; (b) there's a typical sequence of events; (c) there's flight or attempted flight; and (d) furtive movements are present.

  ASSOCIATION WITH KNOWN CRIMINALS -- This is not sufficient by itself for probable cause, except with some crimes, like conspiracies, counterfeiting, food stamp fraud, etc., where it's probable that others are involved or benefitting from the criminal activity. Association with a known drug dealer can also be incriminating in some cases. The most common case would involve somebody acting as security or a lookout for another, and this would be part of the experienced police officer standard.

  PAST CRIMINAL CONDUCT -- An officer's personal knowledge of a suspect's past would be considered more likely to establish probable cause than just knowing they had a rap sheet. The officer would most likely have to know fairly intimate details of the person's life (perhaps by having previously arrested or interrogated them). In most cases, however, knowledge of this information is considered by the law to be relevant, but not sufficient.

  FAILURE TO PROTEST -- This is, again, a presumption. Innocent people would react more strongly to various police actions that are incriminating. It definitely cannot be used alone as a basis of probable cause, but the interesting thing about it is that the police have it both ways. A person who is acting extremely submissive or extra "nice" might also be someone who has something to hide.

• Indirect Sources of Probable Cause (Hearsay Evidence)

  Hearsay is any second-hand information. The most common situation involves informants. The history of Informant Law has evolved from:

  Aguilar test (1964) -- A two-prong test requiring the affidavit spell out the underlying circumstances of how the informant gained their knowledge AND a statement of the informant's veracity, or record of truthfulness.

  Spinelli test (1969) -- A three-prong test requiring all the elements of Aguilar plus an assessment of how accurate the information from the informant might be from a police perspective. Is it against the informant's best interests, for example, to tell the police?

  Gates test (1983) -- This replaces both Aguilar-Spinelli tests with a totality of circumstances test, requiring the police to think both like an offender as well as a reasonable man (subjective and objective test). The totality of circumstances test is discussed under the Stop & Frisk lecture, so it's a much looser standard associated more with reasonable suspicion than probable cause.

Definitions of Probable Cause |