SOUND RECORDINGS AS EVIDENCE
IN COURT PROCEEDINGS
By Steve Cain
Prosecutor Magazine - September/October 1995 by Steve Cain
INTRODUCTION FEDERAL RULE OF EVIDENCE 901 (A) PROVIDES in general terms
that the requirement of authentication or identification as a condition
precedent to the admissibility of evidence is satisfied by proffered proof
sufficient to support a finding that the matter in question is what its
proponent claims it to be. A foundation for authentication of sound recordings
was established in the federal courts in United States v. McKeever,*1*
and upheld in cases such as United States v. McMillan.*2* In McMillan
the court ruled that where a government agent testified that he heard
the voice .of an informant at all times when he was making a recording
of a telephone conversation, that this part of the conversation was accurate,
and that immediately after the telephone calls were completed, a tape
was replayed by the agent in the informant's presence to verify that the
conversation had in fact been recorded and that the instruments were operating
correctly, it was sufficiently established that the recordings were true
and accurate as a basis for their admission in evidence.
In United States v. Kandiel,*3* the court ruled that any question concerning
the credibility of a witness who identifies voices on a tape recording
admitted into evidence simply goes to the weight which the jury accords
the evidence, not its admissibility.
Referring to McMillan the court said:
Applying [the McMillan case], we conclude that the government laid a proper
foundation for introduction of the two cassette tapes into evidence. The
tapes were found at appellant's home. Ahmed Kandiel [defendant's brother]
testified that the tapes were made in Egypt and sent to appellant by their
mother and father while Ahmed was living with appellant. The contents
of the tape recordings have numerous references to people, places and
activities that were corroborative of other testimony in the record. We
believe the government has offered sufficient circumstantial evidence
to establish the prima facie authenticity and correctness of the tapes.
Furthermore we find that the government sufficiently established the
identity of the speakers through the testimony of Ahmed Kandiel. Appellant's
argument that Ahmed's credibility was suspect, and that therefore his
testimony was insufficient to establish foundation for the admission of
the tapes is with out merit. Identification of a voice, whether heard
firsthand or through mechanical or electronic transmission or recording,
may be made "by opinion based upon hearing the voice at any time
under circumstances connecting it with the alleged speaker." Fed.
R. Evid. 901(b)(5). Any question concerning the credibility of the identifying
witness simply goes to the weight the jury accords this evidence, not
to its admissibility. United Statesv. Kirk, 534 E2d 1262, 1277 (8th Cir.
1976), cert. denied, 433 U.S. 907, 97 S. Ct. 2971, 53 L. Ed. 2d 1091 (1977).
Our review of the record convinces us that the district court did not
abuse its discretion in finding that proper foundation was laid for admitting
the tapes. See United States v. Johnson, 767 E2d 1259, 1271 (8th Cir.
The cases are, therefore, now in general agreement as to what constitutes
a proper foundation for the admission of a sound recording and indicate
a reasonably strict adherence to the rules prescribed for testing admissibility
of recordings, as set forth in McMillan.*5*
These rules can be summarized as follows:
The recording device must have been capable of taking the conversation
now offered in evidence
The operator of the device must be competent to operate the device
The recording must be authentic and correct
Changes, additions or deletions have not been made in the recording
The recording must have been preserved in a manner that is shown to
The speakers must be identified
The conversation elicited was made voluntarily and in good faith, without
any kind of inducement.*6*
THE BASIC PROCESS
OVER THE PAST 35 YEARS, ATTORNEYS HAVE UTILIZED THE basic process set
forth in McMillan to create cases for admission of tapes or, on the opposition
side, to deny admission of tape evidence.
This process involves the following elements:
Capability of the recording device:
this first requisite may be fulfilled simply. The very existence of the
tape recording proves that the recording device was functioning and capable
of duplicating sounds.*7*
Competency of the operator:
today most people know how to operate a tape recorder so this step is
almost automatic. In United States v. McCowan,*8* the agent merely testified
that he learned how to use the recorder on the day he made the tapes.
The fact that he successfully made the recordings satisfied the competency
Authenticity and correctness of the recording:
authentication is satisfied by evidence sufficient to support a finding
that the matter in question is "what its proponent claims,*9* as
decreed in Federal Rule of Evidence 901. The standard for correctness
of a recording is whether "the possibility of misidentification and
adulteration [is] eliminated, not absolutely, but as a matter of reasonable
Preservation of the recording with no additions, deletions or changes:
an aural overview of the tape allows the court to hear signs (i.e., gaps)
which might indicate tampering. If there exist signs of tampering, a forensic
expert is often consulted. If there are no signs of tampering, a proper
chain of custody documentation may suffice.*11*
Chain of custody:
this fifth step has created stumbling blocks for proponents of admissibility.
The proponent for the tape's admittance can assure the court that the
item offered as evidence is substantially the same as it was originally
by documenting its "chain of custody." A proper chain of custody
begins with consecutively numbered and dated tapes. Careful logs are then
kept which note the time of particular conversations and the locations
on the tapes at the time of occurrence. These evidence tapes are sealed
and stored in separate envelopes and appropriate chain of custody records
are maintained by the evidence custodian. *12*
Identification of the speakers:
Federal Rule of Evidence 901(b)(5) states that: "Voice identification
is adequate if made by a witness having sufficient familiarity with the
speaker's voice." The rule goes on to clarify that familiarity may
be obtained previous to or after listening to the recorded voice. This
standard for voice identification has been upheld in cases such as United
States v. Rizzo, United States v. Bonanno, and United States v. Hughes)*13*
Voluntary elicitation of the recorded conversation:
as long as one participant in the conversation is aware that he is being
recorded, the tape fulfills this final requirement. This means that a
defendant's Fourth Amendment rights are not violated when the conversation
is electronically monitored by a government agent with consent of the
government informant in the investigation.*14*
ADMISSIBILITY OF INAUDIBLE SOUND RECORDINGS
IT IS A GENERAL RULE THAT A sound recording is admissible unless the inaudible
portions or omissions are so substantial as to render the recording as
a whole untrustworthy as evidence.*15* It has further been established
that the question of admissibility of audible portions of tape recordings,
when certain portions were inaudible, was properly addressed to the discretion
of the-trial court.*16*
RECENT COURT RULINGS
THE HISTORICAL PROCESS SET OUT ABOVE, AS FIRST ESTABLISHED in United States
v. McMillan, is widely used today even though several recent court decisions
provide more relaxed rulings on admissibility.
For example, in United States v. Traficant*17* the court stated that:
"Recent cases have developed more flexible standards for the admission
of tape recorded conversations. The most important criterion for admission
is that the tapes accurately reflect the conversation which they purport
to record .... This evidence may be circumstantial or direct, real or
testimonial, and need not conform to any particular mode." Therefore,
according to the more liberal admission rulings, a tape recording may
be admitted into evidence if a proper chain of custody is proven. Or,
if the chain is not strong enough, the proponent of the tape may submit
it to a qualified forensic expert for authentication. In United States
v. King,*18* the United States Court of Appeals for the Ninth Circuit
characterized the elements of the process as "useful, but not dispositive
guidelines for determining when a proper foundation for the introduction
of sound recordings has been made." The Ninth Circuit said that the
trial court, in the exercise of its discretion, must be satisfied that
the recording is accurate, authentic and generally trustworthy.
EXAMINATION REQUESTS AND REQUIRED EQUIPMENT
WHEN AN AUDIO TAPE IS SUSPECTED OF HAVING BEEN TAMPERED with, it may be
forwarded to a qualified forensic audio specialist for authentication.
Prosecutors often request investigation of deficiencies in the previously
Examples of such problems are:
Credibility questions relating to the tape recorder operator
Differences between the content of the tape and testimony of what was
Most often, however, a forensic expert is contacted when the tape is
believed to have been altered or tampered with. Due to the nature of the
allegations surrounding tampering issues, the examiner will requirements
specific items from the party.
The Federal Bureau of Investigation, for example, has a protocol of required
The original tape
The tape recorders and related components used to produce the recording
Written records of any damage or maintenance done to the recorders, accessories
and other submitted equipment
A derailed statement from the person or persons who made the recording,
describing exactly how it was produced and the conditions that existed
at the time, such as:
1. Power source, including a portable generator or drycell batteries
2. Input, such as telephone, radio frequency transmitter/receiver, miniature
3. Environment, such as telephone transmission line, restaurant, apartment,
4. Background noises, such as television, radio, unrelated conversations,
computer games, etc.
5. Foreground information, such as number of individuals involved in the
conversation, general topics of discussion, closeness to microphone, etc.
6. Magnetic tape, such as brand, format, when purchased, whether previously
7. Recorder operation, such as number of times turned on and off in the
record mode, type of keyboard or remote operations for all known recorded
events, use of voice-activated features, etc.
A typed transcript of the entire recording or, if that is not available,
transcriptions of the portions in question. The items listed above are
examples of what is required by a forensic expert as she begins an examination
of questioned audio recordings.
background voices which at times appear to be as near as the primary voices
(these can, at times, even block the primary voices).
CERTAIN TECHNICAL DEFINITIONS SHOULD BE UNDERSTOOD by prosecutors and
others in considering the technical process of examining sound recordings.
They include the ones listed below.
FALSIFICATION OF TAPES
A QUALIFIED FORENSIC EXPERT DETERMINES AUTHENTICATION by performing a
number of scientific tests which detect evidence of tampering or falsification.
The four basic types of tampering are these:
Deletion: the elimination of words or sounds by stopping the tape and
over-recording unwanted areas
Obscuration: the mixing in of sounds of amplitude sufficient to mask waveform
patterns which originally would show stops and starts in inappropriate
Transformation: the rearranging of words to change con- tent or context
Synthesis: the adding of words or sounds by artificial means or impersonation.
ELECTROMECHANICAL INDICATIONS OF FALSIFICATION
THESE ARE SOMETIMES REFERRED TO AS "ANOMALIES" AND include the
Gaps: segments in a recording which represent unexplained changes in content
or context (a gap can contain buzzing, humming or silence)
Transients: short, abrupt sounds exemplified by clicks, pops, etc. (transients
may indicate tape splicing)
Fades: gradual loss of volume (fades can cause inaudibility and are considered
gaps when the recording becomes fully inaudible)
Equipment sounds: inconsistencies of context caused by the recording equipment
itself (common equipment sounds include hums, static, whistles, and varying
A FORENSIC EXPERT IS TRAINED to detect falsifications and to authenticate
sound recordings. The expert correlates his observations of anomalies
with machine functions to interpret events in the following ways.
Critical listening: this involves the use of human analytical capabilities
to locate anomalies. The forensic expert listens with proper headphones
to the original tape using high-quality analytical equipment. He first
performs a preliminary overview of the original tape and notes events,
including starts, stops, speed fluctuations, and other variations requiring
further investigation. He then examines recorded events and categorizes
them as environmental or non-environmental. After examining recorded events,
the expert analyzes background sounds. He listens for abnormal changes,
absences or the presence of environmental sound. The final phase of critical
listening is an extensive audit of the foreground information. He concentrates
on voices, conversations and other audible sounds. Here anomalies include
sudden changes in a person's voice, abrupt unexplained topic change or
strong foreground interruptions indicative of obscuration. The initial
forensic process of critical listening provides foundation and direction
for later intensive instrumental tests.
Physical inspection: the forensic expert next inspects for tampering with
thorough visual inspection of the tape itself. She inspects the housing
for pry marks, welding, size, label and date, consistent with the alleged
recording date. She also measures the tape and assures that the splicing
of the magnetic tape to the leader is consistent with a normal manufacturing
process. Any other splices are noted as possible alterations.
Magnetic development: direct visual observation of the "developed"
tape is conducted to find track widths, the type of recorder used and
the presence or absence of residual speech signals.
Spectrum analysis: specialized computer equipment and programs to produce
a visual interpretation of a frequency- versus-amplitude and frequency-versus-amplitude-versus-time
displays. This allows the expert to view the entire spectrum or to zoom
in on an area of particular interest thereby helping to characterize the
acoustic quality of anomalies and identify their source.
Waveform analysis: a computer generated display representing time-versus-amplitude
of recorded sounds in graphic form. With such analysis the expert can
often measure signal return time, which reveals how long a recorder had
been turned off. He can identify record- mode events, including the measurement
of record-to- erase-head distance, determination of the spacing between
gaps in multiple-gap erase heads and inspection of the signature shape
and spacing of various record event signals.
Recorder performance: various electrical and mechanical measurements of
standard and modified recorders for use in finding possible origins of
buzz sounds, hum, etc.
IN ORDER TO SUBMIT SOUND RECORDINGS AS EVIDENCE IN court, a prosecutor
or other attorney must establish that the tape is an authentic representation
of the conversation it is said to record. The traditional method of establishing
authenticity involves maintaining a chain of custody which logs all persons,
times and locations concerned in the creation of the tape. Then, the tape
must be officially sealed and stored to complete a proper chain of custody.
However, even if this procedure is strictly observed, there may still
be challenges to the tape's authenticity.
The recording may contain inconsistencies suggestive of tampering. In
such cases, a prosecutor may consult a qualified forensic examiner to
inspect the tape. The examiner would initially listen critically for signs
such as gaps, transients fades, equipment sounds or extraneous voices
which indicate tampering. Then she would utilize other methods like physical
inspection, magnetic development, spectrum analysis and waveform analysis
to discover anomalies.
It is relatively easy to change the content of a recording by deleting
words or sections, by obscuring meaning with over-recorded sounds, or
by transforming context through rearrangement of selected phrases or by
adding additional words through synthesis. Nevertheless, falsifications
normally leave detectable magnetic and waveform acoustic signatures which
can lead to forensic individualization of the evidential recorders and
1 United States v. McKeever, 169 E Supp. 426, 430 (S.D.N.Y. 1958), rev'd
on other grounds, 271 E2d 669 (2d Cir. 1959).
2 United States v. McMillan, 508 E2d I01,104 (8th Cir. 1974), cert. denied,
42 1 U.S. 916 (1975); see also United States v. Kandiel, 865 E2d 967,973-974
(8th Cir. 1988), cert. denied, 487 U.S. 1210 (1988); Todisco v. United
States, 298 E2d 208 (9th Cir. 1962).
3 United States v. Kandiel, 865 E2d 967,973-974 (8th Cir. 1988),cert.
denied, 487 U.S. 1210 (1988).
4 Kandiel, 865 E2d at 974.
5 McMillan, 508 E2d at 104.
6 Id. at 104.
7 United States v. Moss, 591 E2d 428, 433 (8th Cir. 1979); United States
v. McCowan, 706 E2d 863 (8th Cir. 1983).
8 McCowan, 706 E2d at 863.
9 Zenith Radio Corp. v. Matsushita Electrical Industries Co., 505 E Supp.
1190 (E.D. Pa. 1980), and Finance Co. of America v. Bankamerica Corp.,
493 E Supp. 895 (D.C. Md. 1980).
10 Gass v. United States, 416 E2d 767,770 (D.C. Cir. 1969); United States
v. Haldeman, 559 E2d 31 (D.C. Cir. 1976).
11 United States v. Faurote, 749 E2d 40 (7th Cir. 1984).
12 United States v. Craig, 573 E2d 455 (7th Cir. 1977), cert. denied,
439 U.S. 820 (1978).
13 United States v. Rizzo, 492 E2d 443 (2d Cir. 1974), cert. denied, 417
U.S. 944 (1974); United States v. Bonanno, 487 E2d 654 (2d Cir. 1973);
United States v. Hughes, 658 E2d 317 (5th Cir. 1981).
14 United States v. White, 401 U.S. 745 (1971); United States v. Bonanno,
487 E2d 654 (2d Cir. 1973); United States v. Bishton, 463 E2d 887 (D.C.
Cir. 1972); United States v. Quintana, 457 E2d 874 (10th Cir. 1972), cert.
denied, 409 U.S. 877 (1972); United States v. Holmes, 452 E2d 249 (7th
Cir. 1971), cert. denied, 405 U.S. 1016 (1972).
15 United States v. West, 948 E2d 1042 (6th Cir. 1991); People v. Rogers,
543 N.E.2d 300 (Ill. 1989); State v. Rodfiguez, 583 N.E.2d 795 and. 1972).
16 United States v. Enright, 579 E2d 980 (6th Cir. 1978); United States
v. Gordon, 688 E2d 42 (8th Cir. 1982).
17 United States v. Traficant, 558 E Supp. 996, 1002 (N.D. Ohio, 1983).
18 United States v. King, 587 E2d 956, 961 (9th Cir. 1978).