indirect evidence examples forensics

Malicious activity. In Ye Olden Days of the United States, we could ignore the rest of the world, and encode all of our characters into a 7-bit code called ASCII (see https://en.wikipedia.org/wiki/ASCII#Code_chart). For an N-bit number, the two’s complement is equal to 2^N - the number. Here, we assume it is true that b follows from a because we perceive that to be the case repeatedly. Regardless, it is important to realize that digital evidence should not be considered as absolute fact when it is found (as one might consider DNA evidence), but that does not make it weaker than other types of circumstantial evidence. opportunity? In our scenario, an inductive investigator makes the claim: From my repeated experience, I hypothesize that Microsoft Word always automatically fills in a document’s properties with the author’s personal information; therefore, we can infer that this document is a instance of my hypothesis and was created while Adams was at Acme. Jane’s public Web page is found in that history cache, and it is used as indirect evidence that he knew Jane before the crime took place. Inductive Reasoning: the investigator reasons about the crime by what is observed to be true independent of the case. So 150 in decimal is 96 in hex. All the knowledge and skills that can be gained from the study of forensics can be use malicious purposes to invade your privacy. Network data is usually big endian. reconstruction of a crime scene involves forming a hypothesis of the sequence of events from before the crime scene was committed through its commission, means? This viewpoint is quite pessimistic! Along with other processes for verification, corroboration, and validation, the raw information is converted to intelligence. 11 (the base 2, that is, binary notation). Digital evidence is often modifiable. Direct evidence establishes a fact. As you saw (or will see) in the second homework assignment, sometimes we choose to interpret a byte (or bytes) as characters. how a detective will try to reconstruct a crime scene using the documented evidence and any eye witness accounts of the crime. Press CTRL-D (or on Windows, CTRL-Z) to exit the interpreter, then if needed, use python3 or python3.5 to get the right version: The interpreter runs in a REPL: a Read-Eval-Print Loop, which is excellent for exploratory programming. Logs from John’s email server may indicate he checked or sent email at the time when the Web page was retrieved; if he admits to keeping his account and password secret from others, then the email server logs indicate it was he at the keyboard at the time. Third, circumstantial evidence can lead to direct evidence. The answer is yes. You can start the python interpreter by typing python at the command line: But notice on this machine, python defaults to Python2, not Python3. - Hamlet. How do we display these values succinctly? Usually we prefix hex values with 0x, so we’d write it as 0x96 (and if you type this into a python interpreter, it will give you back the value 150, since numbers are displayed by default in base 10). The same sequence of bits can mean different things in different context, and different sequences can mean the same thing in others. Individual characteristics narrow down the evidence to a single, individual source. Copyright © 2019 Marc Liberatore | Instead, they are stored in a format called “two’s complement”. For example, there are more crimes and criminals than law enforcement can handle and investigations often have to be prioritized. For example, if a fingerprint or hair found at the crime scene matches […] First, numerical integer data is typically stored as signed or unsigned. Criminal investigators have the most restrictions on their actions, and their results will come under the most scrutiny, whether as part of a prosecution or a defense. The hex value 0x41, for example, decodes to the integer 65, but under ASCII is also the code for an uppercase A. For a given scenario where it appears that a entails b, an abductive investigator assumes that given that a is true, then b is true. Circumstantial evidence is any evidence that requires some reasoning or inference in order to prove a fact. The skills you will learn can be applied in many different scenarios. Investigators From a legal perspective, “direct” evidence is directly observable and speaks for itself – direct evidence proves a fact without inference. Start it from the command line using something like jupyter notebook; the exact command may vary depending upon how you installed it. In short, if the first byte of a character has the high bit set, it’s a multi-byte character that is decoded according to rules you can read about in the spec or on Wikipedia’s UTF-8 page. Leary’s examination of the evidence relating to Tom Woodson covers all three basic types: direct, indirect, and negative. When a state or federal law are allegedly violated, investigators must follow specific procedures for gathering evidence including the use of warrants or subpoenas. You can also compute it quickly by taking the ones’ complement (the “normal” definition of complement) and then adding one. (This announcement will go away after add/drop ends.). Rarely will the results be used in a criminal or civil proceedings. You’re going to reimplement this program in python for assignment 2. Mostly. In a civil lawsuit, indirect evidence is used more frequently and often more successfully due to the lower burden of proof. In reality, an investigation’s hypothesis often starts this way, but it is not a line of reasoning that is worth testifying over. Jupyter is a nice way to use Python interactively, too. Same story here, it turns out: we need some context to decide what a sequence of bits (or bytes) means. Which of these three types of reasoning did you apply to formulate and justify a hypothesis of Adams’s alleged crime? Finally, a hypothesis is supported that best explains the events that took place. Indirect evidence : evidence providing only a basis for inference about the disputed fact INDIRECT EVIDENCE DOES NOT PROVE A FACT!! There’s one more complication: endianness. A deductive investigator assumes a general truth a, and derives b as a consequence. Was your reasoning based on the presence of the serial number; in real life would you have verified that the particular camera stamped each photo with its serial number? In bits, it is: (128 + 16 + 4 + 2), or you can ask python (bin(150)). Primary role of each member of an investigative scene (about 6), Law-enforcement officer = (first there) secure the scene, Difference between crime-scene investigator and detective, Investigator's document and collect evidence, Priorities of a first responder at a crime scene, POLICE - restrict access to area & log who goes in and who goes out of the crime scene, Seven S's of a crime scene, description & who does what, 1) Secure the scene = POLICE - keep witnesses involved safe like if they need medical attention, Loccard's Principle, when a person comes in contact with an object or another person, a cross-transfer of physical material can occur. First, most evidence at a crime scene is indirect evidence. The primary limitation is that digital evidence is often circumstantial — it is indirect evidence of an event, and we can infer a fact from its presence. Finally, we note that the most conservative view of inductive reasoning is that the investigator’s theory can only be negative – much like the traditional scientific method where we can at best reject the null hypothesis. In scenarios where private wrongs (torts) are alleged and compensation is desired from one party by another, private investigators and attorneys may be hired to bring a case to civil court. But within a multi-byte value, which is the low-order byte and which is the high-order byte? In any case, two-byte integer values are in some programming languages called “short”s; four-byte values are usually the default type for ints, and eight-byte values are called longs. Types of Evidence . Read the lecture notes online and/or get them from a friend. Moreover, when presented with indirect evidence, suspects may be persuaded to confess to a crime. Anyway, many but not all data formats specify the endianness of bytes they store explicitly, but some vary based upon the local CPU’s architecture – whenever you are examining binary data, you need to keep the endianness of the data in mind. If the high-order (“bigger”) bytes some first in the left-to-right reading, we call it “big endian” (as in, big end first). For example, we might represent the number three as: Or, we might see the character “I” and, without more context, not know whether it’s referring to “oneself” or the number one, or something else entirely. However, it is important to understand that more often than not, the complete facts are hidden from the investigator and although a hypothesis fits, it does not mean it is correct. Examples of direct evidence include photos, video, recorded sound, DNA, and human witnesses to an event. Forensics is a science when inductive reasoning is used. Why do some systems use one and some the other? They are not stored as a 7-bit unsigned value with a 1-bit positive-or-negative bit. and software to determine what can be said with assurance about evidence. In “hex” as it’s sometimes called, we represent each byte (8-bits) as two hexadecimal characters. When unauthorized access to a computer system or a collection of data is alleged, the investigator’s work is typically to identify the technical mechanism or human action that was violated so that systems or processes can be repaired to prevent future incidents. No matter what, within a byte, we have an obvious low and high order bit. A byte is eight bits, so a integer stored in an unsigned byte is stored exactly how you’d expect, paralleling the way we write base-10 numbers. What about two byte (16 bit) values, or larger? John’s browser will record when exactly John last visited Jane’s page, and such facts can be corroborated by examining the Web server that hosts Jane’s Web page. For example: I observe that the document properties contain Acme’s name, and it is likely that such information was filled in by Microsoft Word automatically when the document was created at Acme; therefore, this document was created while Anne was at Acme. Validation Standards and Technology (NIST), and by industry and academic researchers in peer-reviewed journals and conference proceedings. For example, we can be sure that the theory that Adams created the document at some third company is false if she never stepped foot in that company’s door. In general, all forms of evidence have class or individual characteristics. The process begins when an investigator has judged that an alleged crime or other event is worth investigating. Deductive Reasoning: the investigator reasons about the crime by constructing truths based on axiomatic assumptions. If the low-order bytes come first, we call it “little endian”. why? STRENGTH IN NUMBERS - The more circumstantial evidence there is, … We did not use the content of the photo as direct evidence; we used information recorded in the EXIF tags to infer its origin. A quick overview of some useful things to know about Python. Representing them as strings of 0s and 1s is unwieldy and hard to manage.

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