Handcuffing the Cops: Miranda's Harmful Effects on Law Enforcement

Policy Reports | Crime

No. 218
Saturday, August 01, 1998
by Paul G. Cassell

Confession Rates and Miranda

Figure I - Confession Rate Changes

Immediately after Miranda, a handful of researchers attempted to measure the effects of the decision. The studies generally suggested significant reductions in the number of suspects giving confessions under the new rules. For a recent article in the Northwestern Law Review, I exhaustively canvassed the empirical evidence on Miranda's social costs in terms of lost criminal cases.5 Examining direct information - before-and-after studies of confession rates in the wake of the decision - I concluded that Miranda significantly depressed the confession rate.6 For example, in 1967:

  • Research revealed that confession rates in Pittsburgh fell from 48 percent of suspects questioned by detectives before the decision to 29 percent after.7
  • New York County District Attorney Frank Hogan testified before the Senate Judiciary Committee that confessions fell even more sharply in his jurisdiction, from 49 percent before Miranda to 14 percent after.8

The Decline in Confessions. Virtually all of the studies just after Miranda found that confession rates had declined, as shown in Figure I. The sole exception was a study in Los Angeles, which has been revealed to be badly flawed.9

"Confession rates fell by about 16 percentage points after Miranda."

The reliable data from the before-and-after studies10 show that confession rates fell by about 16 percentage points after Miranda. In other words, if the confession rate was 60 percent before Miranda, it was 44 percent after - meaning that in about one of every six criminal cases Miranda resulted in a lost confession. The reliable studies also indicate that confessions are needed in about 24 percent of all cases to obtain a conviction. Combining these two figures produces the result that about 3.8 percent (16% x 24%) of all criminal cases in this country are lost because of the restrictions imposed by Miranda.11 Extrapolating across the country, each year there are 28,000 fewer convictions for violent crimes, 79,000 fewer for property crimes and 500,000 fewer for crimes outside the FBI crime index.

"Because of the restrictions, there are 28,000 fewer convictions for violent crimes, 79,000 fewer for property crimes and 500,000 fewer for other crimes each year."

Studying Long-Term Effects. These estimates of Miranda's harmful effects come solely from before-and-after studies that rely on data from the months immediately preceding and following Miranda. The studies accordingly fail to capture Miranda's long-term effects, effects that would reflect criminal suspects' full understanding of the protection Miranda offers them. To gain a better view of Miranda's historic effects, we need some solid statistical indicator that extends beyond 1967 and, indeed, into the 1990s.

In theory, the ideal study would review confession rates since 1967 to see whether, despite initial declines after the decision, the rates have since "rebounded" - in other words, a before-and-after study of confession rates over several decades rather than several months. Unfortunately, no such statistics exist. The only figures that do exist were gathered by individual researchers for particular cities on a one-time basis. Although broad generalizations are hazardous, confession rates before Miranda were probably 55 percent to 60 percent.12 After Miranda, the few studies available reveal lower confession rates. The most recent empirical study, in 1994 in Salt Lake County, Utah, found an overall confession rate of only 33 percent.13 [See Figure II.]

Figure II - Salt Lake County Confession Rates

"Confessions are needed to obtain convictions about onefourth of the time."

Richard Leo's 1993 study from Berkeley, Calif., found an in-custody questioning success rate by detectives of 64 percent. If we adjust this figure for comparability with earlier studies, it translates into an overall confession rate of about 39 percent.14 A 1979 National Institute of Justice study of Jacksonville, Fla., and San Diego, Calif., reported confession rates of 33 percent and 20 percent, respectively. When statements admitting presence at a crime scene are added, the overall rates for incriminating statements rise to 51 percent and 37 percent, respectively.15 A 1977 study of six cities reported a confession rate of 40 percent.16

Taken together, these studies suggest that confession rates have been lower since Miranda. But this conclusion, too, could be attacked on the grounds that studies from individual cities may not be applicable across the country. Because no national data exist, we must search for an alternative measure.

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