MODULE No.11: Measurements in Forensic Examination-I

Transcription

1 SUBJECT Paper No. and Title Module No. and Title Module Tag MODULE No. 11: Measurements in Forensic Examination-I FSC_P1_M11

2 TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 2.1 Ancient Tools and Units of Measurements 2.2 Units of Measurements (English System) 3. Forensic Metrology 4. International Organization for Standardization 5. International SI System of Units 5.1 The Base Units 5.2 Measuring the Base Units Measuring Length 6. Summary

3 1. Learning Outcomes After studying this module, you shall be able to Know Ancient Tools and Measurements. Units of Measurements Forensic Metrology 2. Introduction 2.1 Ancient Tools and Units of Measurements: One of the most important skills which early human beings developed was the ability to measure. According to one belief, people learned to measure much before they learnt to write; and it was with the capability to measure that people learned to count. During the Peking and Neanderthal periods, people carved tools out of natural materials. Gradually, they learnt to determine the right length or weight required for a specific determination, which was mainly hunting in those times. A tool that worked well became the model and standard for developing more tools. Gradually, the methods of measurement and tools became more and more sophisticated; and were converted into measuring sticks. Initially, some very interesting methods were used to do the measurements, e.g. various body parts such as fingers, hands, arms, legs were help to measure distance. Weights was measured with the help of certain containers which a individual or animal could pull. Since human being has ten fingers that can be used to count tens, diverse procedures were framed to connect dissimilar units with different body parts. Time was measured through the phases of the sun, moon, and other heavenly bodies.when it was required to match the capabilities of containers like gourds or clay or metallic vessels, they were full with plant seeds and were then calculated to measure the volumes. Some of the familiar early units of measurement areas follows: Inch - the width of the thumb Digit - the width of the middle finger (about 3/4 inch) Palm - the width of 4 fingers (about 3 inches)

4 Span - the distance covered by the spread hand (about 9 inches) Foot - the length of the foot. Later expressed as the length of 36 -barleycorns taken from the middle of the ear (about 12 inches) Cubit - distance from the elbow to the tip of the middle finger (about 18 inches) Fig-1. Yard - distance from the middle of the body to the fingertips of the outstretched arm (about 36 inches). Fathom- distance spanned by the out stretched arms (about 72 inches) These units had a grave limitation that is related with uncertainty about the body size, which vary among individuals. Such variations resulted in difficulty to establish standards. When individuals worked in a group, mostly the leader of the group would use his body parts as the parameters. Any measurement would be matched to the standards of the size of his body parts. Early civilizations kept working in order to set up various systems of weights and measures. As the international interchange of goods and communication of ideas was limited in those times, it is not astonishing that diverse systems were developed for the same resolution and became recognized in diverse parts of the world - even in diverse parts of the same country. 2.2 Units of Measurements (English System): The measurement scheme generally used in the United States even today is almost the similar as that of was brought to them by the colonists of England. These procedures has their roots in assorted cultures like Babylonian, Roman, Egyptian, Anglo-Saxon, and Norman French. The ancient digit, palm, span and cubic units of length slowly lost their preferences to other set of length units such as inch, foot, and yard (Table-1).

5 The Yard is used as a measure of length that could be marked back to initial Saxon kings. The word yard came from the Saxon word gird which means the boundary of an individual s waist. Those people used to wear a girdle around their waist which could be easily detached and used as an appropriate measuring tool. Other units which American commonly used are the gallon presently has one description in the imperial organization, and two definitions (liquid and dry) in the US customary scheme. A gallon is a measure of volume mostly used in the United States and many other English communicating countries. Other countries use "liters" - the metric unit of measure for volume. Various types of Gallons available- US liquid, US dry and UK and value in terms of liter is shown in table-1 Table-1 Shows conversion of Gallon in to Liters S. No. 1 1 UK Gal Liters 10 Pounds 4.54 Kg (62 0 F or 17 0 C) 2 1 US Gal Liters 8.34 Pounds 3.78 Kg (62 0 F or 17 0 C) 3 1 UK Gal Liters The imperial gallon (UK Gal) The imperial gallon or UK Gallon now defined as exactly litres, that is used in some commonwealth countries and was originally grounded on the volume of 10 pounds (approximately 4.54 kg) of water at 62 0 F or 17 0 C (Table-1). The imperial liquid ounce is defined as of an imperial gallon; there were four quarts in a gallon, two pints in a quart, and 20 fluid ounces in an imperial pint. The US liquid Gallon The US gallon, that is equivalent to exactly liters, is officially well-defined as 231 cubic inches. A US fluid gallon of water weighs around 8.34 pounds or 3.78 kilograms at 62 F (17 C), forming it about 16.6% lighter than the imperial gallon. The US dry Gallon This gallon is equivalent to accurately cubic inches or Liters. The US dry gallon is not used in commerce, and is not recorded in the applicable statute, which excites from the dry quart to the peck.

6 Intricate unit of volume in the metric method, Liters of water weigh up one kilogram. Scientific community of most of the countries other than US uses common metric system. 3. Forensic Metrology Forensic Science being multi-disciplinary in nature has different branches in forensic science laboratories. One of the important division of Forensic Science Laboratory, the services of which are used by almost all other branches, is named Forensic metrology which deals with measurements.the word Metrology comes from Greek μέτρον (metron), means "measure" + λόγος (logos), which means amongst others; speech, oration, discourse, quote, study, calculation, and reason. In Ancient Greek, the term μετρολογία (metrologia) means theory of ratios. The applications of forensic metrology may include the reconstruction of an accident case Oran expert measuring the length of skidmarks and yaw marks to determine the speed of a vehicle. Measuring theblood alcohol concentration has also long been a thoughtful subject with drunken driving prosecutions. The quantity of measured materials (both in relations of their total weights and purity), or determining the length of firearm barrels are other substances which are enclosed by this branch. Metrologists, however, accept that there is an inevitable and inherent component of uncertainty in every measurement- made either at the scene of crime or in the laboratory. A number of measurements and tests are conducted in any Forensic Science Laboratory in order to analyze the evidences in both civil and criminal cases. Forensic Science being interdisciplinary in nature, the analysis ranges widely from DNA sequencing to electron microscopy; to the manual matching of footprints, finger prints, lip prints and tool marks etc. One problem which can hamper a forensic analysis is samples which are degraded, incomplete or presented only in very small amount. It is thus vital for the forensic scientists to procure the complete array of measurements tools required to ensure best results. The scientists thrust their exertions to measure uncertainties, which means that even for the most cautiously performed measurements, the value can never be exactly precise, it is only an estimated value.thus measuring uncertainty and error rates plays an vital role in the forensic examination.

7 4. International Organization for Standardization Recently, plenty of devotion has been given to forensic metrology and metrological traceability as a result of international efforts to accredit Forensic Science Laboratories according to the requirements of International Organization for Standardization International Organization for Standardization also known as ISO, established on 23rd February 1947, is an International Standard-setting body comprising of the representatives from various standard organizationsof different nations. This organization supports worldwide proprietary; industrial and commercial standards. It has its headquarters in Geneva, Switzerland, and as of 2013, it works in 164 countries. The three official languages of the ISO are English, French, and Russian as its name will have abbreviated differently in different languages ( IOS inenglish, OIN in French, etc.). The association accepted as its abbreviated name "ISO", which is imitative from the Greek word isos (ἴσος, meaning equal). Both the name ISO and the logo are recorded logos, and their use is limited. 5. International SI system of Units During 1866, in United States, it turns out to be legal all over the United States of America to hire the weights and measures of the metric method in all contracts, dealings or court proceedings. However, in 1875 an international contract, called as the Meter Pact, set up well-known metric criteria for length and mass and recognized long-lasting mechanisms to mention and accept further modifications in the metric system. This agreement commonly called as the "Treaty of the Meter in the United States, was engaged by 17 countries, comprising the United States. Number of nation increased to 35 in 1900 including the major nations of continental Europe and most of South America-- had officially accepted the metric system. The General Conference on Weights and Measures (1960) adopted an extensive revision along with simplification of the system. Seven base units -- the meter (to measure length), the kilogram (to measure mass), the second (to measure time), the ampere (to measure electric current), the kelvin (to measure thermodynamic temperature), the mole (to measure amount of substance), and the candela (to measure luminous intensity) --were established. The name Systeme International d' Unites (International System of Units), with the international abbreviation SI, was adopted for this modern metric system.

8 1988 Amendments to the Act designated the metric system as the preferred system of weights and measures for United States trade and commerce. After this amendment the measurement science continues to develop more precise and easily reproducible ways to define the measurement units. The General Conference meets periodically to ratify improvements in SI system in years 1964, , 1971, 1975, 1979, 1983, 1991, and Presently, all the forensic measurements in the laboratory investigations are supported by reference standards which are traceable to the International System of Units (SI) maintained by the International Bureau of Weights and Measures. Examples of instruments and equipments used in forensic metrology include breath analyzer, balances & scales, rulers, calipers, Gas chromatographers, and centrifuges etc. Units can be divided into two types: Base Units Derived Units 5.1 The Base Units Quantities Measured Unit - Symbol Length meter - m Mass - kilogram - kg Time second - s Units related to Thermodynamic Temperature kelvin - K Amount of substance mole - mol Electric current - ampere - A Luminous intensity- candela - Cd

9 The five base units which are useful in general chemistry are defined as follows: 1. The meter (m) and the centimeter (cm): A metre was originally measured to be one ten-millionth of the distance from the North Pole to the equator along the meridian running near Dunkirk, Paris, and Barcelona. It was redefined in 1971 as the length of path traveled by light in a vacuum during the time interval of 1/ second. A centimetre, a smaller unit of length, is equal to onehundredth of a meter. 2. The kilogram (kg) and the Gram (g): A kilogram is the mass of a particular cylinder made of platinum-iridium alloy. It is known as the International Prototype Kilogram. It is kept at the International Bureau of Weights and Measures in Serves, France. It was derived from the mass of a cubic decimeter of water.one gram equals one thousandth (1/1000) of a kilogram. 3. The second (s) It was originally defined as 1/86,400th of a mean solar day. It was redefined in 1967 as the duration of 9,192,631,770 periods of the radiation which corresponds to the transition between two hyperfine levels of the fundamental state of a cesium-133 atom. 4. The kelvin (K) It is 1/ of the temperature interval between absolute zero and the triple point of water (the temperature at which ice, liquid water, and water vapor are in equilibrium). The -Celsius scale is derived from the -Kelvin scale. An interval of 1 K is equal to 1 C. 5. The mole (mol) It is the amount of substance which contains as many entities as there are atoms in exactly kg of carbon-12. This number is known as Avogadro s number which has a value of x 1023 per mole *6.3 x 1017 (determined by U.S. National Bureau of Standards in 1974). 5.2 Measuring the Base Units Measuring Length: To measure length as a distance and use the metric ruler and/or the metric tape to measure the length, width, and height of the objects in question.

10 Fig-3 Scale to Measure Distance Converting inches in to centimeters and feet into meters is a regular practice in mathematics and science. The following few conversions which are commonly used are shown in table-2. Technically, only one conversion is required, but sometimes it is easier to use the one which is closer to the values of our requirement. Table-2 English System Measurements to Measure Distances S.No lines = 1 inch 2 12 inches = 1 foot 3 3 feet = 1 yard yards = 1 mile 5 36 inches = 1 yard yards = quarter-mile yards = half-mile links = 1 chain 9 10 chains = 1 furlong 10 8 furlongs = 1 mile 11 4 inches = 1 hand yards = 1 chain yards = 1 rod, pole or perch 14 4 poles = 1 chain poles = 1 furlong

11 Instead of having a large number of units of different sizes, such as inches, feet, years, fathoms, furlongs, and miles etc. in the English system; it was decided to use prefixes which would multiply the base units by multiples of tens for larger measurements and decimal fractions for smaller measurements. According to the metric system, the basis of length units for the metric system is the meter. This name was derived from the Greek word metron meaning "a measure." The physical standard representing the meter was to be constructed so that it would equal to one ten-millionth of the distance from the North Pole to the equator along the meridian running near Dunkirk in France and Barcelona in Spain. A meter is almost the same length as one yard. The metric system is based on units of ten, which means: 1 centimeter = 10 millimeters 1 meter = 100 centimeters = 1,000 millimeters 1 kilometer = 1,000 meters = 100,000 centimeters = 100,000,000 millimeters = 1*108 millimeters The surface area of a cube can be calculated by adding together the surface area (length x width) of all six sides. The volume of a cube is equal to (length x width x height). Table-3 Showing other Popular Conversions used to Measure Distances in Meters Serial No. 1 1 Inch = 2.54 centimeters = 25.4 millimeters 2 1 foot = centimeters 3 1 yard = 0.91 meters 4 1 mile = 1.6 kilometers 5 1 millimeter = 0.04 inches 6 1 centimeter = 0.39 inches = feet 7 1 meter = 3.28 feet 8 1 kilometer = 0.62 miles

12 6. Summary 1. Some very interesting methods were used to do the measurements, e.g. various body parts such as fingers, hands, arms, legs were used to measure distance. 2. These units had a grave limitation that is related with uncertainty about the body size, which vary from person to person. 3. The applications of forensic metrology may include the reconstruction of an accident case Oran expert measuring the length of skid marks and yaw marks to determine the speed of a vehicle. Measuring the blood alcohol concentration has also long been a serious issue with drunken driving prosecutions. 4. One problem which can hamper a forensic analysis is samples which are degraded, incomplete or presented only in very small amount. 5. Presently, all the forensic measurements in the laboratory investigations are supported by reference standards which are traceable to the International System of Units (SI) maintained by the International Bureau of Weights and Measures.